ARM: S5P: Add s5p_reset_hook() for perform reset using SWRESET on S5P SoCs

This patch adds s5p_reset_hook() which includes software reset
by using SWRESET.

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