msm: mdss: Update ad_bl_level on first set backlight call

Upon first set backlight call when bl_updated has been
set ad_bl_level needs to be updated to the current backlight
level. Adding the change to update it.

Change-Id: I285332613ffcc1d6c94247b7c9bd89f054c80d4c
Signed-off-by: Ping Li <pingli@codeaurora.org>
(cherry picked from commit 180390069d044fee9328a97579d71c70a74c92a1)