msm_fb: display: wait4vsync after timing generator is turned off

When continuous splash is enabled, timing generator is enabled at
bootloader, it then needs to be turned off at mdp4_dsi_video_on()
to switch displayed content from frame buffer. wait4vsync after
timing generator is turned off is necessary to make sure DMAP has
finished fetching splash logo from original splash buffer. Otherwise,
DMAP iommu page fault may happen.

Change-Id: I35f9fb9da76f93b60d4719d147aea3246c770c9f
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
msm_fb: display: wait4vsync before set suspend flag

Since wait4vsync checks suspend flag, wait4vsync needs to
be executed before suspend flag set to enforce wait happen.
Also, when timing generator is turned off, wait4vsync can
not be used anymore since the last vsync may have passed
before wait4vsync called. This patch fixed commit_comp
timeout cause fence timeout happen on hdmi plug and unplug
cases.

CRs-fixed: 449027
Change-Id: I0f5520538bb290643a648c937296b6bc097fe051
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>