KVM: selftests: aarch64: Add vGIC library functions to deal with vIRQ state

Add a set of library functions for userspace code in selftests to deal
with vIRQ state (i.e., ioctl wrappers).

Signed-off-by: Ricardo Koller <ricarkol@google.com>
Acked-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211109023906.1091208-6-ricarkol@google.com