msm_fb: display: Add MSMFB_OVERLAY_COMMIT ioctl.

MSMFB_OVERLAY_COMMIT ioctl is used to display on external.
This is used instead of the default PAN mechanism to avoid delays in that path.
This ioctl for external also waits for DMAE thus fixing tearing.

Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Signed-off-by: Arun Kumar K.R <akumarkr@codeaurora.org>