irqchip/apple-aic: Register vgic maintenance interrupt with KVM

In order to deliver vgic maintenance interrupts that Nested Virt
requires, hook it into the FIQ space, even if it is delivered
as an IRQ (we don't distinguish between the two anyway).

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230103095022.3230946-4-maz@kernel.org


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>