hwc: Push a dummy -1 release fence in case of flush

In case of flush no release fence is pushed to hwc_layer queue and
no error is returned to f/w, so it could end up requesting release
fences. In such a case the queue can be emptied and from the next
valid cycle we end up giving the same cycle's release fence back.
Push a dummy -1 fence to avoid this.

Change-Id: I1330d0b47a23df3203c06cc23aa4b6b4a6fe669e
CRs-fixed: 1114808
1 file changed