refactor(gic): add a is_feat_gic_supported() standard helper

FEAT_GIC is a CPU feature like any other, add an arch_features.h helper
for it.

Change-Id: I762b6333907f5f3dd3352544c1f2fb211a794b3e
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
7 files changed