feat(fvp): introduce PLATFORM_TEST_RAS_FFH config

feat(fvp): introduce PLATFORM_TEST_RAS_FFH config

While doing RAS related tests there were few patches related with
fault injection and handling were applied through CI hooks.
These patches were invisible as they were applied and removed after the
build is done.

This patch introduces build macro PLATFORM_TEST_RAS_FFH and moves the
patches applied through CI under this.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Iddba52f3ebf21f575a473e50c607a944391156b9