sdm: Allow draw cycle in doze state.

- Check for on/doze states while validating states during a
  prepare/commit phase. Allow updates in these two states.
- Send draw cycle only with FB target to SDM in place of Flush.
- Avoid flush if there is no buffer successfully submitted to SDM
  after Off state.
- Make flush no-op for virtual display.

CRs-Fixed: 931331

Change-Id: I9e5f52abb81decef1b90a8d132ef35b80093cb0e
10 files changed