irqchip: mips-gic: Remove gic_map_to_pin()

Remove the gic_map_to_pin() function in favour of using the new
write_gic_map_pin() accessor function which isn't any more complex to
use & allows us to drop a level of abstraction.

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/17032/


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