msm: mdss: Avoid vysnc wait when PCC and DDIC update backlight

Remove wait for vsync in display commit if both PCC and DDIC
need to update for external backlight feature.

Change-Id: I57aeb48acba24e0ca3fff21b1117e48fe452028b
Signed-off-by: Xu Yang <yangxu@codeaurora.org>
Signed-off-by: Abhijith Desai <desaia@codeaurora.org>