sdm: Set vsync_registered_ to false in SetEventState

Set vsync_registered_ to false in SetEventState. In the chance
that HandleVsync does not get called by driver, we may fall in
state where vsync_registered_ never updates to false.

CRs-Fixed: 2615875
Change-Id: I033e46d9b79e0ffc320ff89c7847fb6d9ba12421
1 file changed