KVM: arm64: selftests: Add support to disable and enable local IRQs

Add functions local_irq_enable() and local_irq_disable() to
enable and disable the IRQs from the guest, respectively.

Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211007233439.1826892-9-rananta@google.com