docs: GCC toolchain upgrade to version 9.2-2019.12

This toolchain provides multiple cross compilers and are publicly
available on developer.arm.com

We build TF-A in CI using:
AArch32 bare-metal target (arm-none-eabi)
AArch64 ELF bare-metal target (aarch64-none-elf)

Change-Id: I910200174d5bad985504d1af4a1ae5819b524003
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>

docs/getting_started/initial-build.rst

@@ -8,13 +8,13 @@ Performing an Initial Build
 
    .. code:: shell
 
-       export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-
+       export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-none-elf-
 
    For AArch32:
 
    .. code:: shell
 
-       export CROSS_COMPILE=<path-to-aarch32-gcc>/bin/arm-eabi-
+       export CROSS_COMPILE=<path-to-aarch32-gcc>/bin/arm-none-eabi-
 
    It is possible to build TF-A using Clang or Arm Compiler 6. To do so
    ``CC`` needs to point to the clang or armclang binary, which will
@@ -32,7 +32,7 @@ Performing an Initial Build
 
    .. code:: shell
 
-       export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-
+       export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-none-elf-
        make CC=<path-to-armclang>/bin/armclang PLAT=<platform> all
 
    Clang will be selected when the base name of the path assigned to ``CC``
@@ -43,7 +43,7 @@ Performing an Initial Build
 
    .. code:: shell
 
-       export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-
+       export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-none-elf-
        make CC=<path-to-clang>/bin/clang PLAT=<platform> all
 
 -  Change to the root directory of the TF-A source tree and build.

docs/getting_started/prerequisites.rst

@@ -26,7 +26,7 @@ Toolchain
 |TF-A| can be built with any of the following *cross-compiler* toolchains that
 target the Armv7-A or Armv8-A architectures:
 
-- GCC >= 8.3-2019.03 (from the `Arm Developer website`_)
+- GCC >= 9.2-2019.12 (from the `Arm Developer website`_)
 - Clang >= 4.0
 - Arm Compiler >= 6.0
 

docs/plat/arm/fvp/index.rst

@@ -223,7 +223,7 @@ address ``0x82000000``, the firmware can be built like this:
 
 .. code:: shell
 
-    CROSS_COMPILE=aarch64-linux-gnu-  \
+    CROSS_COMPILE=aarch64-none-elf-  \
     make PLAT=fvp DEBUG=1             \
     RESET_TO_BL31=1                   \
     ARM_LINUX_KERNEL_AS_BL33=1        \

docs/plat/arm/juno/index.rst

@@ -136,7 +136,7 @@ a single FIP binary. It assumes that a Linaro release has been installed.
 
       .. code:: shell
 
-          export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-linux-gnu-
+          export CROSS_COMPILE=<path-to-aarch64-gcc>/bin/aarch64-none-elf-
 
    -  The following parameters should be used to build BL1 and BL2 in AArch64
       and point to the BL32 file.