irqchip: mips-gic: Remove gic_present

Nothing uses the global gic_present variable anymore; mips_gic_present()
should be used instead. Remove the dead code.

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/17045/


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