MIPS: JZ4740: register an irq_domain for the interrupt controller

MIPS: JZ4740: register an irq_domain for the interrupt controller

When probing the interrupt controller, register an IRQ domain such
that the interrupts can be translated by devicetree code & thus used
from devicetree.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: Brian Norris <computersforpeace@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/10140/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>