ARM: EXYNOS4: Update HRT for supporting PM

This patch updates HRT driver for supporting PM.
The resume function of PWM4 timer which is used clocksource is needed
when kernel is resuming for restarting.

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