msm: mdss: serialize dynamic fps and dynamic bit clock updates

Dynamic refresh update and dynamic bit clock switch cannot happen
on the same vsync boundary. Serialize them in the commit thread
to avoid vsync timeout issues.

Change-Id: I55077eca7415bf307ddd30040024b3716a78f6fd
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>