ARM: S3C24XX: add support for second irq set of S3C2416

The S3C2416 has a separate second interrupt register-set to support
additional irqs. This patch adds the necessary constants and registers
the irq handlers for it.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>