msm_fb: display: add stage commit before kickoff to WFD

Since stage commit had been splited out of stage up fucnction,
it needed to be called to stage pipes into mixer befroe
kickoff mixer. Add this function into overlay writeback for WFD.
This patch varies a little bit from the mainline patch as it got
updated again. Now making it equivalent to mainline.

(cherry picked from commit e540ed2d72f723d3b5ac7e444899921cc227ff63)

Change-Id: Ic2bf488ef61d6c31a3997906b2d70090818a9bc0
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Signed-off-by: Siddhartha Agrawal <agrawals@codeaurora.org>

Conflicts:

	drivers/video/msm/mdp4.h