arm: Make sure not to shift off of the end of a uint32_t in KVM.

arm: Make sure not to shift off of the end of a uint32_t in KVM.

The methods which set or get an attribute from the virtual GIC use a
shift constant which is 32, but they store their result in a 32 bit
variable and, according to clang, are used to shift 32 bit inputs. This
is undefined behavior in terms of the shift, and will truncate off the
value regardless.

Change-Id: Ie9543ab9e6e1d5f86317a9210d220928b23ffaf8
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23129
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>