arm: gic: Register irqdomain after adding it

Recently a change was added to break apart irq_domain_add() into
two functions. The first creates the domain, and the second
registers it.

This change abides to this new interface and registers the
GIC irq_domain after creating it.

Change-Id: I34c6a1f56dc27113a9b72f0fefa577276f91bbc8
Signed-off-by: Michael Bohan <mbohan@codeaurora.org>
diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
index a6b5d0b..770a376 100644
--- a/arch/arm/common/gic.c
+++ b/arch/arm/common/gic.c
@@ -858,6 +858,7 @@
 	domain->priv = gic;
 	domain->ops = &gic_irq_domain_ops;
 	irq_domain_add(domain);
+	irq_domain_register(domain);
 
 	gic_chip.flags |= gic_arch_extn.flags;
 	gic_dist_init(gic);