kvm, arm: Add parameter to force simulation of Gicv2

kvm, arm: Add parameter to force simulation of Gicv2

By setting simulate_gic to True it will be possible to prevent
the simulation from using the host interrupt controller

Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Change-Id: I7c7df798e07bfaddbc2f1e7dd981b6aff621a9d1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36795
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Hsuan Hsu <kugwa2000@gmail.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>