irqchip/gic: Mark gic_init_physaddr() static

We get 1 warning when building kernel with W=1:
drivers/irqchip/irq-gic.c:917:13: warning: no previous prototype for 'gic_init_physaddr' [-Wmissing-prototypes]

In fact, this function is only used in the file in which it is
declared and don't need a declaration, but can be made static.
so this patch marks this function with 'static'.
Signed-off-by: NBaoyou Xie <baoyou.xie@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-gic.c

@@ -939,7 +939,7 @@ unsigned long gic_get_sgir_physaddr(void)
 	return gic_dist_physaddr + GIC_DIST_SOFTINT;
 }
 
-void __init gic_init_physaddr(struct device_node *node)
+static void __init gic_init_physaddr(struct device_node *node)
 {
 	struct resource res;
 	if (of_address_to_resource(node, 0, &res) == 0) {