msm: pm: Adjust for events with hard wakeups

Get the next event and setup a new timer to expire
earlier than the next event after accounting for the
latency of the low power state being entered. This
will ensure that the core is active to handle the event
when it arrives.

Change-Id: Ife3e165bc6b61e0109c692cf4675baef0f4290f0
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>