rtc: alarm: Add power-on alarm feature

Android does not support powering up of phone through alarm.
Adding shutdown hook in alarm driver which will set alarm while phone
is going down so as to power-up the phone after alarm expiration.

CRs-Fixed: 432312
Change-Id: I21786d264b93f7c0c660823a0a1a221c1b4df7b2
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>
rtc: alarm: Set power-on alarm 120 sec before actual alarm time

This will add extra buffer time for booting-up the device before
actual alarm expiration time.

Change-Id: I02cad84c394a6aab943fff37a1a0de56bb511f56
Signed-off-by: Mohit Aggarwal <maggarwa@codeaurora.org>
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>