Convert the Renesas RZ/A1 Interrupt Controller Device Tree binding
documentation to json-schema.

Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>