ARM: EXYNOS: fix software reset logic for EXYNOS5440 SOC

This patch fixes software reset logic. Software reset applies only to
powered-on domains in SOC because software reset to all domains causes
reboot failure.

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