irqchip: mips-gic: Remove platform irq_ack/irq_eoi callbacks

There's no need for platforms to have their own GIC irq_ack/irq_eoi
callbacks.  irq_ack need only clear the GIC's edge detector on
edge-triggered interrupts and there's no need at all for irq_eoi.
Also get rid of the mask_ack callback since it's not necessary either.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Reviewed-by: Qais Yousef <qais.yousef@imgtec.com>
Tested-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jeffrey Deans <jeffrey.deans@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Jonas Gorski <jogo@openwrt.org>
Cc: John Crispin <blogic@openwrt.org>
Cc: David Daney <ddaney.cavm@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/7809/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>