MIPS/IRQCHIP: Move Ingenic SoC intc driver to drivers/irqchip

Move the driver for Ingenic SoC interrupt controllers into
drivers/irqchip where it belongs.

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/10147/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>