cpu-kvm: Initialize _hasKernelIRQChip in the constructor

cpu-kvm: Initialize _hasKernelIRQChip in the constructor

This class member was only correctly set to true when using an in-kernel
interrupt controller, but was un-initialized when trying to use a user-
space one and would cause trouble.

JIRA: https://gem5.atlassian.net/browse/GEM5-663

Change-Id: I71b052c6da7e8790b05a15c07e7933bc4f912785
Signed-off-by: Hsuan Hsu <hsuan.hsu@mediatek.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30917
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>