KVM: selftests: aarch64: Add tests for IRQFD in vgic_irq

Add injection tests for the KVM_IRQFD ioctl into vgic_irq.

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/20211109023906.1091208-16-ricarkol@google.com