docs(build): update GCC to version 11.2-2022.02

This toolchain provides multiple cross compilers and is 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: Ia14de2c7d9034a6f0bc56535e961fffc81bcbf29
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
1 file changed