icnss: Prevent suspend while processing events

Power collapsing while processing events posted to work queue
causes stability issues because of suspending while in the
process of bring-up, bring-down or recovery. Prevent suspend
while processing events by calling pm_stay_awake().

CRs-fixed: 1073854
Change-Id: I6c7ae3b6e52529b14075fb2212bc2c5f76ae5730
Signed-off-by: Prashanth Bhatta <bhattap@codeaurora.org>