config/rdfremont*: scp: set compiler path for aarch64 host

Aarch64 linux host version of gcc 9.2.1 arm none eabi  which gets
installed via apt repo in Ubuntu doesn't support compiling Arm-v8M
cores. Compiling of Arm-v8M is required to build SCP repo which includes
building of LCP firmware. So, pass aarch64 linux host version of gcc
11.2 arm none eabi to build on aarch64 host.

Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>
Change-Id: Iff18e3e57062a1b829d0343db4c57b7e99c7e4bc