irqchip: mips-gic: Simplify gic_local_irq_domain_map()

Simplify gic_local_irq_domain_map() by:

- Moving the check for invalid IRQs outside of the loop.

- Moving the decision about whether to use gic_cpu_pin or timer_cpu_pin
  outside of the loop.

- Using the new write_gic_vo_map() accessor function to avoid the need
  to handle each map register separately.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17027/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>