irqchip/mips-gic: Use gic_vpes instead of NR_CPUS

NR_CPUS is set by Kconfig and could be much higher than what actually is in the
system.

gic_vpes should be a true representitives of the number of cpus in the system,
so use it instead.

Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Cc: <jason@lakedaemon.net>
Cc: <marc.zyngier@arm.com>
Cc: <jiang.liu@linux.intel.com>
Cc: <linux-mips@linux-mips.org>
Cc: <lisa.parratt@imgtec.com>
Cc: Qais Yousef <qsyousef@gmail.com>
Link: http://lkml.kernel.org/r/1449580830-23652-15-git-send-email-qais.yousef@imgtec.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>