GCC: Upgrade to version 9.2-2019.12 of toolchain

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

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

Change-Id: I2360a3ac6705c68dca781b85e9894867df255b3e
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/docs/plat/marvell/build.rst b/docs/plat/marvell/build.rst
index c10bcff..d0e37c6 100644
--- a/docs/plat/marvell/build.rst
+++ b/docs/plat/marvell/build.rst
@@ -9,7 +9,7 @@
 
     .. code:: shell
 
-        > export CROSS_COMPILE=/path/to/toolchain/aarch64-linux-gnu-
+        > export CROSS_COMPILE=/path/to/toolchain/aarch64-none-elf-
 
 (2) Set path for FIP images: