alarmtimer: Program mpm wakeup time in milliseconds

Currently, mpm wakeup time is programmed in seconds
due to which there is a possibility that wakeup
happens later than the expected time. This patch
fixes the issue by programming the mpm wakeup time
in milliseconds.

CRs-Fixed: 2010001
Change-Id: I5c4905a0386e60ae54876f30d89f445fd06a161c
Signed-off-by: Mohit Aggarwal <maggarwa@codeaurora.org>