clocksource/drivers/mips-gic-timer: Make gic_compare_irqaction static

Fix sparse warning:

drivers/clocksource/mips-gic-timer.c:70:18: warning:
 symbol 'gic_compare_irqaction' was not declared. Should it be static?
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: <daniel.lezcano@linaro.org>
Link: https://lkml.kernel.org/r/20190322144359.19516-1-yuehaibing@huawei.com

drivers/clocksource/mips-gic-timer.c

@@ -67,7 +67,7 @@ static irqreturn_t gic_compare_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-struct irqaction gic_compare_irqaction = {
+static struct irqaction gic_compare_irqaction = {
 	.handler = gic_compare_interrupt,
 	.percpu_dev_id = &gic_clockevent_device,
 	.flags = IRQF_PERCPU | IRQF_TIMER,