arch-arm, dev-arm: WakeRequest implementation

arch-arm, dev-arm: WakeRequest implementation

This patch provides a GIC WakeRequest implementation based on GICv3 and
FVPBasePwrCtrl models. When GICR_WAKER.ProcessorSleep is set to 1 for a
certain PE, any pending interrupt coming from the Redistributor asserts
a WakeRequest signal; if PwrStatus.WEN is set, this brings up the PE.

Change-Id: I5e8b7f0e9f7706dfcc7d2e0857f4c3b86cdc04ca
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26810
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>