ARM platform can have a non-contiguous GICR frames. For instance, a
multi socket platform can have two or more GIC Redistributor frames
which are 4TB apart. Hence it is necessary for the `gicv3_rdistif_probe`
function to probe all the GICR frames available in the platform.

Introduce `plat_arm_override_gicr_frames` function which platforms can
use to override the default gicr_frames which holds the GICR base
address of the primary cpu.

Change-Id: I1f537b0d871a679cb256092944737f2e55ab866e
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>