KVM: selftests: aarch64: Move gic_v3.h to shared headers

Move gic_v3.h to the shared headers location. There are some definitions
that will be used in the vgic-irq test.
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/20211109023906.1091208-2-ricarkol@google.com