ARM: S5PV310: Add IRQ support

This patch adds IRQ support for S5PV310.
ARM GIC is installed in S5PV310 instead of VIC which is in every other CPUs
in S5P series. Several irq combiners are used to resolve the lack of irq
lines in current implementation.

Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
Signed-off-by: Hyuk Lee <hyuk1.lee@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>