hwc2: Fix validation reset from QDCM CMD Handler

QDCM Command Handler doesn't run in same thread as HWC main thread.
The validation reset from this thread needs to wait on the Sequence
Scope lock, so that the validate state of display doesn't get reset
between the Validate and Present phase of the current draw cycle.

CRs-Fixed: 2342280
Change-Id: I1c311ab40d4f7886129782ab15c05a8051dfd80a
1 file changed