ARM: S5P: Add Support common arch_reset() for S5P

This patch adds support common arch_reset() for
S5P6440, S5P6442, S5PC100 and S5PV210/S5PC110.
Now perform reset using Watchdog reset, SWRESET
support with s5p_reset_hook() will be added later.

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