KVM: arm64: nv: Add Maintenance Interrupt emulation

Emulating the vGIC means emulating the dreaded Maintenance Interrupt.

This is a two-pronged problem:

- while running L2, getting an MI translates into an MI injected
  in the L1 based on the state of the HW.

- while running L1, we must accurately reflect the state of the
  MI line, based on the in-memory state.

The MI INTID is added to the distributor, as expected on any
virtualisation-capable implementation, and further patches
will allow its configuration.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250225172930.1850838-11-maz@kernel.org


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