dt-bindings: interrupt-controller: Convert MSI controller to json-schema

Split the MSI controller bindings from the MSI binding document
into DT schema format using json-schema.

Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Link: https://lore.kernel.org/r/20210921183420.436-2-kettenis@openbsd.org


Signed-off-by: Rob Herring <robh@kernel.org>