Revert "Revert "msm_fb: display: allow backlight update after first update""

This reverts commit a07ba467cf89dddec2e168a5af00e26ced9219ba.
video: msm: Fix initial state of LCD backlight

 * For devices which use the LCD backlight (such as D2), we need
   to actually call the function which sets the brightness after
   initializing it in the probe.

Change-Id: Id6b7c0de3cd31181394c56c7f6061bca9defd861