dt-bindings: interrupt-controller: convert icpu intr bindings to json-schema

Convert device tree bindings for Microsemi Ocelot SoC ICPU Interrupt
Controller to YAML format

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201125103206.136498-2-gregory.clement@bootlin.com