msm: mdss: scale backlight before setting to panel from commit

From display commit a backlight set call is done through the
update backlight function that would not scale the backlight
before sending it to panel. Hence there are possibilities of
backlight jumps which can cause flickers. Fix by scaling the
backlight with bl_scale before sending to panel.

Change-Id: I173f699657575f74885d76a36e8e7d8d8636bd36
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>
Signed-off-by: Gopal G Goberu <ggober@codeaurora.org>