sdm: Clear solid fill stages upon flush

Solid fill stages persist after empty commit because the property
DIM_STAGES_V1 is set during solid fill creation but not cleared
by HWDeviceDRM::Flush(). This commit clears solid fill stages and
updates the property.

CRs-Fixed: 2348615
Change-Id: I017b44094286f89c315d16e0de6717f6ffae7b76
2 files changed