msm_fb: display: Send vsync events using sysfs for MDP4 targets

Replace sending of vsync timestamp using uevents with sysfs entry
as uevent result in increase in power numbers due to broadcast in
nature. Also, for smart panel, wait4vsync is removed.

(cherry picked from commit ca47ab601b9d36b2a96685a6e93042318ebbba8b)

Change-Id: I96577a3408fa0e2e1b54cf97434ddcf75bee589c
Signed-off-by: Mayank Chopra <makchopra@codeaurora.org>
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Signed-off-by: Jessica Gonzalez <jgaona@codeaurora.org>

Conflicts:
	drivers/video/msm/mdp4_overlay_dsi_cmd.c
	drivers/video/msm/mdp4_overlay_dsi_video.c
	drivers/video/msm/mdp4_overlay_dtv.c
	drivers/video/msm/mdp4_overlay_lcdc.c
	drivers/video/msm/msm_fb.c