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In order to quantify the overall time spent in the PSCI software
implementation, an initial collection of PMF instrumentation points
has been added.

Instrumentation has been added to the following code paths:

- Entry to PSCI SMC handler.  The timestamp is captured as early
  as possible during the runtime exception and stored in memory
  before entering the PSCI SMC handler.

- Exit from PSCI SMC handler.  The timestamp is captured after
  normal return from the PSCI SMC handler or if a low power state
  was requested it is captured in the bl31 warm boot path before
  return to normal world.

- Entry to low power state.  The timestamp is captured before entry
  to a low power state which implies either standby or power down.
  As these power states are mutually exclusive, only one timestamp
  is defined to describe both.  It is possible to differentiate between
  the two power states using the PSCI STAT interface.

- Exit from low power state.  The timestamp is captured after a standby
  or power up operation has completed.

To calculate the number of cycles spent running code in Trusted Firmware
one can perform the following calculation:

(exit_psci - enter_psci) - (exit_low_pwr - enter_low_pwr).

The resulting number of cycles can be converted to time given the
frequency of the counter.

Change-Id: Ie3b8f3d16409b6703747093b3a2d5c7429ad0166
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

When using more than a single service in PMF, it is necessary that the
per-service timestamps begin on a cache line boundary.  Previously it
was possible that two services shared a cache line for their
timestamps.  This made it difficult to reason about cache maintenance
operations within a single service and required a global understanding
of how all services operate.

Change-Id: Iacaae5154a7e19ad4107468e56df9ad082ee371c

The macro calculates an absolute address rather than an offset so
rename it to avoid confusion.

Change-Id: I351f73dfd809fd28c0c30d38928caf5c5cd1af04

Given the service name and timestamp id, this assembler macro
calculates the offset into a memory region where the per-cpu timestamp
value is located.

Change-Id: I47f6dfa2a17be182675e2ca0489d6eed42433209

More headers will be needed soon so better to move these to their own
directory to avoid cluttering include/lib.

Change-Id: I6a72dc5b602d6f51954cf60aadd1beb52a268670