ARM: S5PV310: Add support External Interrupt

This patch adds EINT(External Interrupt) support on S5PV310 and S5PC210.
All EINTs are transferred to GIC through interrupt combiner.

Signed-off-by: Jongsun Han <jongsun.han@samsung.com>
Signed-off-by: Jongpill Lee <boyko.lee@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>