KVM: arm64: selftests: Add basic GICv3 support

Add basic support for ARM Generic Interrupt Controller v3.
The support provides guests to setup interrupts.

The work is inspired from kvm-unit-tests and the kernel's
GIC driver (drivers/irqchip/irq-gic-v3.c).

Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211007233439.1826892-13-rananta@google.com