IRQCHIP: irq_cpu: declare irqchip table entry

Allow the MIPS CPU interrupt controller to be probed from DT using the
generic __irqchip_of_table for platforms which use irqchip_init. This
will avoid such platforms needing to duplicate the compatible string &
init function pointer.

[ralf@linux-mips.org: Resolved conflict due the preceeding commit that
moves irq-cpu.c.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: linux-mips@linux-mips.org
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: linux-kernel@vger.kernel.org
Cc: Felix Fietkau <nbd@openwrt.org>
Patchwork: https://patchwork.linux-mips.org/patch/10131/


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