KVM: arm64: nv: Handle L2->L1 transition on interrupt injection

KVM: arm64: nv: Handle L2->L1 transition on interrupt injection

An interrupt being delivered to L1 while running L2 must result
in the correct exception being delivered to L1.

This means that if, on entry to L2, we found ourselves with pending
interrupts in the L1 distributor, we need to take immediate action.
This is done by posting a request which will prevent the entry in
L2, and deliver an IRQ exception to L1, forcing the switch.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250225172930.1850838-10-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>