ARM: gic: Disable all interrupts before Power collapse

We may enter PC from either suspend or idle path. So even
if we enter from suspend path we should disable all interrupts
before we go to Power collapse, so as to make sure, there
are no pending interrupts(not even the wakeup capable) which
could result in WFI failure.

CRs-Fixed: 363293
Change-Id: Ied25b21f59a9fa0a891a27a2e806876cc337a759
Signed-off-by: Taniya Das <tdas@codeaurora.org>