msm: mdss: Idle off before backlight is on

If there is no backlight control after idle off, backlight level is not
applied properly. So be sure to set the idle off before turning the backight
on.

Change-Id: If05382fa5a2fb651270aae93033ee3bc398e071e
Signed-off-by: Devin Kim <dojip.kim@lge.com>