irqchip/gic-v3: Re-init GIC hardware upon hibernation restore

Code added in this patch takes backup of different set of
registers during hibernation suspend. On receiving hibernation
restore callback, it restores register values from backup. This
ensures state of hardware to be same just before hibernation and
after restore.

Change-Id: I36cfce8901ccfd82562764d8f6614f8760273248
Signed-off-by: Omkar Savagaonkar <omkars@codeaurora.org>
Signed-off-by: Arun KS <arunks@codeaurora.org>