kvm, arm: don't create interrupt events while saving GIC state

kvm, arm: don't create interrupt events while saving GIC state

If an interrupt was pending according to Kvm state during a drain,
the Pl390 model would create an interrupt event that could not be
serviced, preventing the system from draining.  The proper behavior
is for the Pl390 not actively being used for simulation to just skip
the GIC state machine that delivers interrupts.

Change-Id: Icb37e7e992f1fb441a9b3a26daa1bb5a6fe19228
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3661
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>