TF-A GICv2 driver: Introduce makefile

This patch moves all GICv2 driver files into new added
'gicv2.mk' makefile for the benefit of the generic driver
which can evolve in the future without affecting platforms.

NOTE: Usage of 'drivers/arm/gic/common/gic_common.c' file
is now deprecated and platforms with GICv2 driver need to
be modified to include 'drivers/arm/gic/v2/gicv2.mk' in
their makefiles.

Change-Id: Ib10e71bdda0e5c7e80a049ddce2de1dd839602d1
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
9 files changed