This patch provides support for GICv3.1 extended PPI and SPI
range. The option is enabled by setting to 1 and passing
`GIC_EXT_INTID` build flag to gicv3.mk makefile.
This option defaults to 0 with no extended range support.

Change-Id: I7d09086fe22ea531c5df51a8a1efd8928458d394
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

This patch provides separation of GICD, GICR accessor
functions and adds new macros for GICv3 registers access
as a preparation for GICv3.1 and GICv4 support.
NOTE: Platforms need to modify to include both
'gicdv3_helpers.c' and 'gicrv3_helpers.c' instead of the
single helper file previously.

Change-Id: I1641bd6d217d6eb7d1228be3c4177b2d556da60a
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>