Introduce ARM platform APIs for GICv3 Redistributor

As with other ARM platform GIC APIs, these directly invoke the GICv3
driver APIs for Redistributor power management.

For the sake of uniform GIC API, empty stubs are placed for those GIC
drivers that lack Redistributor component.

Change-Id: Iad0d760d4dbca790998f7768cda621ff3b15a864
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/plat/arm/common/arm_gicv3_legacy.c b/plat/arm/common/arm_gicv3_legacy.c
index 8396b60..cbf11fb 100644
--- a/plat/arm/common/arm_gicv3_legacy.c
+++ b/plat/arm/common/arm_gicv3_legacy.c
@@ -94,3 +94,17 @@
 {
 	arm_gic_pcpu_distif_setup();
 }
+
+/******************************************************************************
+ * Stubs for Redistributor power management. Although legacy configuration isn't
+ * supported, these are provided for the sake of uniform GIC API
+ *****************************************************************************/
+void plat_arm_gic_redistif_on(void)
+{
+	return;
+}
+
+void plat_arm_gic_redistif_off(void)
+{
+	return;
+}