msm: pm-stats: add suspend stats reset handling

Add suspend stats reset handling to reset suspend_stats
counters and time when sending the reset command.
"echo reset > /proc/msm_pm_stats"

CRs-fixed: 610602
Change-Id: I80be31815b25ce967b50a1d0f2384250b5438420
Signed-off-by: Anil kumar mamidala <amami@codeaurora.org>