rtc: alarm: Change wake-up source

Currently, RTC_ALARM is used to wake-up target from
suspend state and is also used for power-off alarm
feature. This patch uses qtimer to wake-up from
suspend state.

Change-Id: Ia42cfecd573309be2f03c18b4f1c321be8202d7d
Signed-off-by: Mohit Aggarwal <maggarwa@codeaurora.org>