msm: mdp: Send fake vsync only when enabled from userspace

Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>
msm: mdp: Disable vsync in video off.

Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>

Conflicts:
	drivers/video/msm/mdp4_overlay_dsi_video.c