refactor(gic): prepare for a new GIC revision

The top level interrupt functions that common code calls are generic
enough to become tftf's interrupt API, so rename the file to better
reflect this.  Conversely, gic_common.c is quite specific to GICv2 and
GICv3 so also rename it to reflect this.

Change-Id: I7becd74fae526a3bc5a9ef9501f0db75b1b086fb
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
25 files changed