checks: add interrupts property check

Add a check for nodes with interrupts property that they have a valid
parent, the parent has #interrupt-cells property, and the size is a
valid multiple of #interrupt-cells.

This may not handle every possible case and doesn't deal with
translation thru interrupt-map properties, but should be enough for
modern dts files.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>