refactor(gic): make the GIC driver generic

Every currently supported tftf has some variety of GIC that can work
with the main GIC driver. So there's no need to have each platform
specify that as part of their build.

Change-Id: Ic771aad82e8f423042bcf3bf1d3b70cba6236666
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
17 files changed