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This patch adds an optional API to the platform port:

    void plat_error_handler(int err) __dead2;

The platform error handler is called when there is a specific error
condition after which Trusted Firmware cannot continue. While panic()
simply prints the crash report (if enabled) and spins, the platform
error handler can be used to hand control over to the platform port
so it can perform specific bookeeping or post-error actions (for
example, reset the system). This function must not return.

The parameter indicates the type of error using standard codes from
errno.h. Possible errors reported by the generic code are:

    -EAUTH  : a certificate or image could not be authenticated
              (when Trusted Board Boot is enabled)
    -ENOENT : the requested image or certificate could not be found
              or an IO error was detected
    -ENOMEM : resources exhausted. Trusted Firmware does not use
              dynamic memory, so this error is usually an indication
              of an incorrect array size

A default weak implementation of this function has been provided.
It simply implements an infinite loop.

Change-Id: Iffaf9eee82d037da6caa43b3aed51df555e597a3

This patch is a complete rework of the main Makefile. Functionality
remains the same but the code has been reorganized in sections in
order to improve readability and facilitate adding future extensions.

A new file 'build_macros.mk' has been created and will contain common
definitions (variables, macros, etc) that may be used from the main
Makefile and other platform specific makefiles.

A new macro 'FIP_ADD_IMG' has been introduced and it will allow the
platform to specify binary images and the necessary checks for a
successful build. Platforms that require a BL30 image no longer need
to specify the NEED_BL30 option. The main Makefile is now completely
unaware of additional images not built as part of Trusted Firmware,
like BL30. It is the platform responsibility to specify images using
the macro 'FIP_ADD_IMG'. Juno uses this macro to include the BL30
image in the build.

BL33 image is specified in the main Makefile to preserve backward
compatibility with the NEED_BL33 option. Otherwise, platform ports
that rely on the definition of NEED_BL33 might break.

All Trusted Board Boot related definitions have been moved to a
separate file 'tbbr_tools.mk'. The main Makefile will include this
file unless the platform indicates otherwise by setting the variable
'INCLUDE_TBBR_MK := 0' in the corresponding platform.mk file. This
will keep backward compatibility but ideally each platform should
include the corresponding TBB .mk file in platform.mk.

Change-Id: I35e7bc9930d38132412e950e20aa2a01e2b26801

This patch redefines the values of IO_FAIL, IO_NOT_SUPPORTED and
IO_RESOURCES_EXHAUSTED to match the corresponding definitions in
errno.h:

    #define IO_FAIL                     (-ENOENT)
    #define IO_NOT_SUPPORTED            (-ENODEV)
    #define IO_RESOURCES_EXHAUSTED      (-ENOMEM)

NOTE: please note that the IO_FAIL, IO_NOT_SUPPORTED and
IO_RESOURCES_EXHAUSTED definitions are considered deprecated
and their usage should be avoided. Callers should rely on errno.h
definitions when checking the return values of IO functions.

Change-Id: Ic8491aa43384b6ee44951ebfc053a3ded16a80be

This patch adds an optional API to the platform port:

    void bl1_plat_prepare_exit(void);

This function is called prior to exiting BL1 in response to the
RUN_IMAGE_SMC request raised by BL2. It should be used to perform
platform specific clean up or bookkeeping operations before
transferring control to the next image.

A weak empty definition of this function has been provided to
preserve platform backwards compatibility.

Change-Id: Iec09697de5c449ae84601403795cdb6aca166ba1

When a platform port does not define PLAT_PERCPU_BAKERY_LOCK_SIZE, the total
memory that should be allocated per-cpu to accommodate all bakery locks is
calculated by the linker in bl31.ld.S. The linker stores this value in the
__PERCPU_BAKERY_LOCK_SIZE__ linker symbol. The runtime value of this symbol is
different from the link time value as the symbol is relocated into the current
section (.bss). This patch fixes this issue by marking the symbol as ABSOLUTE
which allows it to retain its correct value even at runtime.

The description of PLAT_PERCPU_BAKERY_LOCK_SIZE in the porting-guide.md has been
made clearer as well.

Change-Id: Ia0cfd42f51deaf739d792297e60cad5c6e6e610b

This patch unifies the bakery lock api's across coherent and normal
memory implementation of locks by using same data type `bakery_lock_t`
and similar arguments to functions.

A separate section `bakery_lock` has been created and used to allocate
memory for bakery locks using `DEFINE_BAKERY_LOCK`. When locks are
allocated in normal memory, each lock for a core has to spread
across multiple cache lines. By using the total size allocated in a
separate cache line for a single core at compile time, the memory for
other core locks is allocated at link time by multiplying the single
core locks size with (PLATFORM_CORE_COUNT - 1). The normal memory lock
algorithm now uses lock address instead of the `id` in the per_cpu_data.
For locks allocated in coherent memory, it moves locks from
tzfw_coherent_memory to bakery_lock section.

The bakery locks are allocated as part of bss or in coherent memory
depending on usage of coherent memory. Both these regions are
initialised to zero as part of run_time_init before locks are used.
Hence, bakery_lock_init() is made an empty function as the lock memory
is already initialised to zero.

The above design lead to the removal of psci bakery locks from
non_cpu_power_pd_node to psci_locks.

NOTE: THE BAKERY LOCK API WHEN USE_COHERENT_MEM IS NOT SET HAS CHANGED.
THIS IS A BREAKING CHANGE FOR ALL PLATFORM PORTS THAT ALLOCATE BAKERY
LOCKS IN NORMAL MEMORY.

Change-Id: Ic3751c0066b8032dcbf9d88f1d4dc73d15f61d8b

This patch adds the necessary documentation updates to porting_guide.md
for the changes in the platform interface mandated as a result of the new
PSCI Topology and power state management frameworks. It also adds a
new document `platform-migration-guide.md` to aid the migration of existing
platform ports to the new API.

The patch fixes the implementation and callers of
plat_is_my_cpu_primary() to use w0 as the return parameter as implied by
the function signature rather than x0 which was used previously.

Change-Id: Ic11e73019188c8ba2bd64c47e1729ff5acdcdd5b

Since there is a unique warm reset entry point, the FVP and Juno
port can use a single mailbox instead of maintaining one per core.
The mailbox gets programmed only once when plat_setup_psci_ops()
is invoked during PSCI initialization. This means mailbox is not
zeroed out during wakeup.

Change-Id: Ieba032a90b43650f970f197340ebb0ce5548d432

The authentication framework deprecates plat_match_rotpk()
in favour of plat_get_rotpk_info(). This patch removes
plat_match_rotpk() from the platform port.

Change-Id: I2250463923d3ef15496f9c39678b01ee4b33883b

This patch extends the platform port by adding an API that returns
either the Root of Trust public key (ROTPK) or its hash. This is
usually stored in ROM or eFUSE memory. The ROTPK returned must be
encoded in DER format according to the following ASN.1 structure:

    SubjectPublicKeyInfo  ::=  SEQUENCE  {
        algorithm           AlgorithmIdentifier,
        subjectPublicKey    BIT STRING
    }

In case the platform returns a hash of the key:

    DigestInfo  ::= SEQUENCE {
        digestAlgorithm     AlgorithmIdentifier,
        keyDigest           OCTET STRING
    }

An implementation for ARM development platforms is provided in this
patch. When TBB is enabled, the ROTPK hash location must be specified
using the build option 'ARM_ROTPK_LOCATION'. Available options are:

    - 'regs' : return the ROTPK hash stored in the Trusted
      root-key storage registers.

    - 'devel_rsa' : return a ROTPK hash embedded in the BL1 and
      BL2 binaries. This hash has been obtained from the development
      RSA public key located in 'plat/arm/board/common/rotpk'.

On FVP, the number of MMU tables has been increased to map and
access the ROTPK registers.

A new file 'board_common.mk' has been added to improve code sharing
in the ARM develelopment platforms.

Change-Id: Ib25862e5507d1438da10773e62bd338da8f360bf

The Trusted firmware code identifies BL images by name. The platform
port defines a name for each image e.g. the IO framework uses this
mechanism in the platform function plat_get_image_source(). For
a given image name, it returns the handle to the image file which
involves comparing images names. In addition, if the image is
packaged in a FIP, a name comparison is required to find the UUID
for the image. This method is not optimal.

This patch changes the interface between the generic and platform
code with regard to identifying images. The platform port must now
allocate a unique number (ID) for every image. The generic code will
use the image ID instead of the name to access its attributes.

As a result, the plat_get_image_source() function now takes an image
ID as an input parameter. The organisation of data structures within
the IO framework has been rationalised to use an image ID as an index
into an array which contains attributes of the image such as UUID and
name. This prevents the name comparisons.

A new type 'io_uuid_spec_t' has been introduced in the IO framework
to specify images identified by UUID (i.e. when the image is contained
in a FIP file). There is no longer need to maintain a look-up table
[iname_name --> uuid] in the io_fip driver code.

Because image names are no longer mandatory in the platform port, the
debug messages in the generic code will show the image identifier
instead of the file name. The platforms that support semihosting to
load images (i.e. FVP) must provide the file names as definitions
private to the platform.

The ARM platform ports and documentation have been updated accordingly.
All ARM platforms reuse the image IDs defined in the platform common
code. These IDs will be used to access other attributes of an image in
subsequent patches.

IMPORTANT: applying this patch breaks compatibility for platforms that
use TF BL1 or BL2 images or the image loading code. The platform port
must be updated to match the new interface.

Change-Id: I9c1b04cb1a0684c6ee65dee66146dd6731751ea5

This patch adds support for SYSTEM_SUSPEND API as mentioned in the PSCI 1.0
specification. This API, on being invoked on the last running core on a
supported platform, will put the system into a low power mode with memory
retention.

The psci_afflvl_suspend() internal API has been reused as most of the actions
to suspend a system are the same as invoking the PSCI CPU_SUSPEND API with the
target affinity level as 'system'. This API needs the 'power state' parameter
for the target low power state. This parameter is not passed by the caller of
the SYSTEM_SUSPEND API. Hence, the platform needs to implement the
get_sys_suspend_power_state() platform function to provide this information.
Also, the platform also needs to add support for suspending the system to the
existing 'plat_pm_ops' functions: affinst_suspend() and
affinst_suspend_finish().

Change-Id: Ib6bf10809cb4e9b92f463755608889aedd83cef5

The attempt to run the CPU reset code as soon as possible after reset
results in highly complex conditional code relating to the
RESET_TO_BL31 option.

This patch relaxes this requirement a little. In the BL1, BL3-1 and
PSCI entrypoints code, the sequence of operations is now as follows:
 1) Detect whether it is a cold or warm boot;
 2) For cold boot, detect whether it is the primary or a secondary
    CPU. This is needed to handle multiple CPUs entering cold reset
    simultaneously;
 3) Run the CPU init code.

This patch also abstracts the EL3 registers initialisation done by
the BL1, BL3-1 and PSCI entrypoints into common code.

This improves code re-use and consolidates the code flows for
different types of systems.

NOTE: THE FUNCTION plat_secondary_cold_boot() IS NOW EXPECTED TO
NEVER RETURN. THIS PATCH FORCES PLATFORM PORTS THAT RELIED ON THE
FORMER RETRY LOOP AT THE CALL SITE TO MODIFY THEIR IMPLEMENTATION.
OTHERWISE, SECONDARY CPUS WILL PANIC.

Change-Id: If5ecd74d75bee700b1bd718d23d7556b8f863546

This patch removes the FIRST_RESET_HANDLER_CALL build flag and its
use in ARM development platforms. If a different reset handling
behavior is required between the first and subsequent invocations
of the reset handling code, this should be detected at runtime.

On Juno, the platform reset handler is now always compiled in.
This means it is now executed twice on the cold boot path, first in
BL1 then in BL3-1, and it has the same behavior in both cases. It is
also executed twice on the warm boot path, first in BL1 then in the
PSCI entrypoint code.

Also update the documentation to reflect this change.

NOTE: THIS PATCH MAY FORCE PLATFORM PORTS THAT USE THE
FIRST_RESET_HANDLER_CALL BUILD OPTION TO FIX THEIR RESET HANDLER.

Change-Id: Ie5c17dbbd0932f5fa3b446efc6e590798a5beae2

Update the User Guide, Porting Guide and Firmware Design documents
to align them with the recent changes made to the FVP and Juno
platform ports.

Also fix some other historical inaccuracies.

Change-Id: I37aba4805f9044b1a047996d3e396c75f4a09176

This patch removes the plat_get_max_afflvl() platform API
and instead replaces it with a platform macro PLATFORM_MAX_AFFLVL.
This is done because the maximum affinity level for a platform
is a static value and it is more efficient for it to be defined
as a platform macro.

NOTE: PLATFORM PORTS NEED TO BE UPDATED ON MERGE OF THIS COMMIT

Fixes ARM-Software/tf-issues#265

Change-Id: I31d89b30c2ccda30d28271154d869060d50df7bf

This patch updates the user-guide.md with the various build options related to
Trusted Board Boot and steps to build a FIP image which includes this
support. It also adds a trusted-board-boot.md which describes the scope and
design of this feature.

Change-Id: Ifb421268ebf7e06a135684c8ebb04c94835ce061

Change-Id: Iaf9d6305edc478d39cf1b37c8a70ccdf723e8ef9

The CPU specific reset handlers no longer have the freedom
of using any general purpose register because it is being invoked
by the BL3-1 entry point in addition to BL1. The Cortex-A57 CPU
specific reset handler was overwriting x20 register which was being
used by the BL3-1 entry point to save the entry point information.
This patch fixes this bug by reworking the register allocation in the
Cortex-A57 reset handler to avoid using x20. The patch also
explicitly mentions the register clobber list for each of the
callee functions invoked by the reset handler

Change-Id: I28fcff8e742aeed883eaec8f6c4ee2bd3fce30df

This patch adds the function plat_match_rotpk() to the platform
porting layer to provide a Root Of Trust Public key (ROTPK)
verification mechanism. This function is called during the
Trusted Board Boot process and receives a supposed valid copy
of the ROTPK as a parameter, usually obtained from an external
source (for instance, a certificate). It returns 0 (success) if
that key matches the actual ROTPK stored in the system or any
other value otherwise.

The mechanism to access the actual ROTPK stored in the system
is platform specific and should be implemented as part of this
function. The format of the ROTPK is also platform specific
(to save memory, some platforms might store a hash of the key
instead of the whole key).

TRUSTED_BOARD_BOOT build option has been added to allow the user
to enable the Trusted Board Boot features. The implementation of
the plat_match_rotpk() funtion is mandatory when Trusted Board
Boot is enabled.

For development purposes, FVP and Juno ports provide a dummy
function that returns always success (valid key). A safe trusted
boot implementation should provide a proper matching function.

Documentation updated accordingly.

Change-Id: I74ff12bc2b041556c48533375527d9e8c035b8c3

This patch adds support to call the reset_handler() function in BL3-1 in the
cold and warm boot paths when another Boot ROM reset_handler() has already run.

This means the BL1 and BL3-1 versions of the CPU and platform specific reset
handlers may execute different code to each other. This enables a developer to
perform additional actions or undo actions already performed during the first
call of the reset handlers e.g. apply additional errata workarounds.

Typically, the reset handler will be first called from the BL1 Boot ROM. Any
additional functionality can be added to the reset handler when it is called
from BL3-1 resident in RW memory. The constant FIRST_RESET_HANDLER_CALL is used
to identify whether this is the first version of the reset handler code to be
executed or an overridden version of the code.

The Cortex-A57 errata workarounds are applied only if they have not already been
applied.

Fixes ARM-software/tf-issue#275

Change-Id: Id295f106e4fda23d6736debdade2ac7f2a9a9053

This patch allows the platform to validate the power_state and
entrypoint information from the normal world early on in PSCI
calls so that we can return the error safely. New optional
pm_ops hooks `validate_power_state` and `validate_ns_entrypoint`
are introduced to do this.

As a result of these changes, all the other pm_ops handlers except
the PSCI_ON handler are expected to be successful. Also, the PSCI
implementation will now assert if a PSCI API is invoked without the
corresponding pm_ops handler being registered by the platform.

NOTE : PLATFORM PORTS WILL BREAK ON MERGE OF THIS COMMIT. The
pm hooks have 2 additional optional callbacks and the return type
of the other hooks have changed.

Fixes ARM-Software/tf-issues#229

Change-Id: I036bc0cff2349187c7b8b687b9ee0620aa7e24dc

This patch removes the non-secure entry point information being passed
to the platform pm_ops which is not needed. Also, it removes the `mpidr`
parameter for  platform pm hooks which are meant to do power management
operations only on the current cpu.

NOTE: PLATFORM PORTS MUST BE UPDATED AFTER MERGING THIS COMMIT.

Change-Id: If632376a990b7f3b355f910e78771884bf6b12e7

This patch extends the build option `USE_COHERENT_MEMORY` to
conditionally remove coherent memory from the memory maps of
all boot loader stages. The patch also adds necessary
documentation for coherent memory removal in firmware-design,
porting and user guides.

Fixes ARM-Software/tf-issues#106

Change-Id: I260e8768c6a5c2efc402f5804a80657d8ce38773

Fixes arm-software/tf-issues#276

This patch adds support for supplying pre-built BL binaries for BL2,
BL3-1 and BL3-2 during trusted firmware build. Specifying BLx = <path_to_BLx>
in the build command line, where 'x' is any one of BL2, BL3-1 or BL3-2, will
skip building that BL stage from source and include the specified binary in
final fip image.

This patch also makes BL3-3 binary for FIP optional depending on the
value of 'NEED_BL33' flag which is defined by the platform.

Fixes ARM-software/tf-issues#244
Fixes ARM-software/tf-issues#245

Change-Id: I3ebe1d4901f8b857e8bb51372290978a3323bfe7

This patch gathers miscellaneous minor fixes to the documentation, and comments
in the source code.

Change-Id: I631e3dda5abafa2d90f464edaee069a1e58b751b
Co-Authored-By: Soby Mathew <soby.mathew@arm.com>
Co-Authored-By: Dan Handley <dan.handley@arm.com>

This patch adds CPU core and cluster power down sequences to the CPU specific
operations framework introduced in a earlier patch. Cortex-A53, Cortex-A57 and
generic AEM sequences have been added. The latter is suitable for the
Foundation and Base AEM FVPs. A pointer to each CPU's operations structure is
saved in the per-cpu data so that it can be easily accessed during power down
seqeunces.

An optional platform API has been introduced to allow a platform to disable the
Accelerator Coherency Port (ACP) during a cluster power down sequence. The weak
definition of this function (plat_disable_acp()) does not take any action. It
should be overriden with a strong definition if the ACP is present on a
platform.

Change-Id: I8d09bd40d2f528a28d2d3f19b77101178778685d

This patch adds an optional platform API (plat_reset_handler) which allows the
platform to perform any actions immediately after a cold or warm reset
e.g. implement errata workarounds. The function is called with MMU and caches
turned off. This API is weakly defined and does nothing by default but can be
overriden by a platform with a strong definition.

Change-Id: Ib0acdccbd24bc756528a8bd647df21e8d59707ff

* Move TSP platform porting functions to new file:
  include/bl32/tsp/platform_tsp.h.

* Create new TSP_IRQ_SEC_PHY_TIMER definition for use by the generic
  TSP interrupt handling code, instead of depending on the FVP
  specific definition IRQ_SEC_PHY_TIMER.

* Rename TSP platform porting functions from bl32_* to tsp_*, and
  definitions from BL32_* to TSP_*.

* Update generic TSP code to use new platform porting function names
  and definitions.

* Update FVP port accordingly and move all TSP source files to:
  plat/fvp/tsp/.

* Update porting guide with above changes.

Note: THIS CHANGE REQUIRES ALL PLATFORM PORTS OF THE TSP TO
      BE UPDATED

Fixes ARM-software/tf-issues#167

Change-Id: Ic0ff8caf72aebb378d378193d2f017599fc6b78f

The intent of io_init() was to allow platform ports to provide
a data object (io_plat_data_t) to the IO storage framework to
allocate into. The abstraction was incomplete because io_plat_data_t
uses a platform defined constant and the IO storage framework
internally allocates other arrays using platform defined constants.

This change simplifies the implementation by instantiating the
supporting objects in the IO storage framework itself. There is now
no need for the platform to call io_init().

The FVP port has been updated accordingly.

THIS CHANGE REQUIRES ALL PLATFORM PORTS THAT USE THE IO STORAGE
FRAMEWORK TO BE UDPATED.

Change-Id: Ib48ac334de9e538064734334c773f8b43df3a7dc

Secure ROM at address 0x0000_0000 is defined as FVP_TRUSTED_ROM
Secure RAM at address 0x0400_0000 is defined as FVP_TRUSTED_SRAM
Secure RAM at address 0x0600_0000 is defined as FVP_TRUSTED_DRAM

BLn_BASE and BLn_LIMIT definitions have been updated and are based on
these new memory regions.

The available memory for each bootloader in the linker script is
defined by BLn_BASE and BLn_LIMIT, instead of the complete memory
region.

TZROM_BASE/SIZE and TZRAM_BASE/SIZE are no longer required as part of
the platform porting.

FVP common definitions are defined in fvp_def.h while platform_def.h
contains exclusively (with a few exceptions) the definitions that are
mandatory in the porting guide. Therefore, platform_def.h now includes
fvp_def.h instead of the other way around.

Porting guide has been updated to reflect these changes.

Change-Id: I39a6088eb611fc4a347db0db4b8f1f0417dbab05

The purpose of platform_is_primary_cpu() is to determine after reset
(BL1 or BL3-1 with reset handler) if the current CPU must follow the
cold boot path (primary CPU), or wait in a safe state (secondary CPU)
until the primary CPU has finished the system initialization.

This patch removes redundant calls to platform_is_primary_cpu() in
subsequent bootloader entrypoints since the reset handler already
guarantees that code is executed exclusively on the primary CPU.

Additionally, this patch removes the weak definition of
platform_is_primary_cpu(), so the implementation of this function
becomes mandatory. Removing the weak symbol avoids other
bootloaders accidentally picking up an invalid definition in case the
porting layer makes the real function available only to BL1.

The define PRIMARY_CPU is no longer mandatory in the platform porting
because platform_is_primary_cpu() hides the implementation details
(for instance, there may be platforms that report the primary CPU in
a system register). The primary CPU definition in FVP has been moved
to fvp_def.h.

The porting guide has been updated accordingly.

Fixes ARM-software/tf-issues#219

Change-Id: If675a1de8e8d25122b7fef147cb238d939f90b5e

This patch adds the CPUECTLR_EL1 register and the CCI Snoop Control
register to the list of registers being reported when an unhandled
exception occurs.

Change-Id: I2d997f2d6ef3d7fa1fad5efe3364dc9058f9f22c

This patch introduces platform APIs to initialise and
print a character on a designated crash console.
For the FVP platform, PL011_UART0 is the designated
crash console. The platform porting guide is also updated
to document the new APIs.

Change-Id: I5e97d8762082e0c88c8c9bbb479353eac8f11a66

This patch removes the allocation of memory for coherent stacks, associated
accessor function and some dead code which called the accessor function. It also
updates the porting guide to remove the concept and the motivation behind using
stacks allocated in coherent memory.

Fixes ARM-software/tf-issues#198

Change-Id: I00ff9a04f693a03df3627ba39727e3497263fc38

Update the "Memory layout on FVP platforms" section in the Firmware
Design document to reflect the overlaying of BL1 and BL2 images
by BL3-1 and BL3-2.

Also update the Porting Guide document to mention the
BL31_PROGBITS_LIMIT and BL32_PROGBITS_LIMIT constants.

Change-Id: I0b23dae5b5b4490a01be7ff7aa80567cff34bda8

 - Add support for loading a BL3-0 image in BL2. Information about
   memory extents is populated by platform-specific code. Subsequent
   handling of BL3-0 is also platform specific.
   The BL2 main function has been broken down to improve readability.
   The BL3-2 image is now loaded before the BL3-3 image to align with
   the boot flow.

 - Build system: Add support for specifying a BL3-0 image that will be
   included into the FIP image.

 - IO FIP driver: Add support for identifying a BL3-0 image inside a
   FIP image.

 - Update the documentation to reflect the above changes.

Change-Id: I067c184afd52ccaa86569f13664757570c86fc48

This concept is no longer required since we now support loading of
images at fixed addresses only.

The image loader now automatically detects the position of the image
inside the current memory layout and updates the layout such that
memory fragmentation is minimised.

The 'attr' field of the meminfo data structure, which used to hold
the bottom/top loading information, has been removed. Also the 'next'
field has been removed as it wasn't used anywhere.

The 'init_bl2_mem_layout()' function has been moved out of common
code and put in BL1-specific code. It has also been renamed into
'bl1_init_bl2_mem_layout'.

Fixes ARM-software/tf-issues#109

Change-Id: I3f54642ce7b763d5ee3b047ad0ab59eabbcf916d

The array of affinity nodes is currently allocated for 32 entries
with the PSCI_NUM_AFFS value defined in psci.h. This is not enough
for large systems, and will substantially over allocate the array
for small systems.

This patch introduces an optional platform definition
PLATFORM_NUM_AFFS to platform_def.h. If defined this value is
used for PSCI_NUM_AFFS, otherwise a value of two times the number
of CPU cores is used.

The FVP port defines PLATFORM_NUM_AFFS to be 10 which saves
nearly 1.5KB of memory.

Fixes ARM-software/tf-issues#192

Change-Id: I68e30ac950de88cfbd02982ba882a18fb69c1445