hwc: commit changes for ext display on blank

- When the device is suspended, the overlay pipes will be unset,
  but they wont be unstaged as there is no DISPLAY_COMMIT ioctl
  called for ext display, as a result the fence wont be signalled
  by the MDP.
- This is needed as we dont turn off the External display(HDMI)

Change-Id: I9794ad2ae7c9d7b4ce3f9787f50ea9da87966e41
CRs-fixed: 425483
1 file changed