dt-bindings: interrupt-controller: Convert snps,dw-apb-ictl to DT schema

Convert the Synopsys DW-APB interrupt controller binding to schema
format. It's a straight-forward conversion of the typical interrupt
controller.

Link: https://lore.kernel.org/r/20250505144842.1292840-1-robh@kernel.org


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