rtc: alarm: update power_on alarm setting logic

The previous power_on alarm value should be checked to avoid
cancelling the alarm by mistake.

CRs-fixed: 551966
Change-Id: I4de12265416fab41a9c591d09961c9fef0d25917
Signed-off-by: Xiaocheng Li <lix@codeaurora.org>
3 files changed