fsl-mc: Add minimal infrastructure to use platform MSI

fsl-mc: Add minimal infrastructure to use platform MSI

Add the tiny bit of infrastructure required to use platform MSI
instead of the current hack. This means providing a write_msi_msg
callback, as well as irq domain and devid retrieval helpers.

Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com> # LX2160ARDB, LS2088ARDB
Tested-by: Sascha Bischoff <sascha.bischoff@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Thomas Gleixner <tglx@kernel.org>
Link: https://lore.kernel.org/r/20260224100936.3752303-3-maz@kernel.org
Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>