msm: pm-8x60: Fix incorrect computation of wakeup times

A incorrect computation of scheduled wakeup times, which is passed on to
RPM for wakeup from deep sleep modes, could result in the Core sleeping
for longer than intended during RPM assisted power collapse.

CRs-fixed: 488889
Change-Id: I26132c402e7839c3700b3d91514dd347dc1d478c
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>