irqchip/gic-v3: Remove gic_root_node variable from the ITS code

The gic_root_node variable defined in ITS driver is not actually
used, so just remove it.
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-gic-v3-its.c

@@ -103,7 +103,6 @@ struct its_device {
 
 static LIST_HEAD(its_nodes);
 static DEFINE_SPINLOCK(its_lock);
-static struct device_node *gic_root_node;
 static struct rdists *gic_rdists;
 
 #define gic_data_rdist()		(raw_cpu_ptr(gic_rdists->rdist))
@@ -1607,8 +1606,6 @@ int its_init(struct device_node *node, struct rdists *rdists,
 	}
 
 	gic_rdists = rdists;
-	gic_root_node = node;
-
 	its_alloc_lpi_tables();
 	its_lpi_init(rdists->id_bits);