bd->props.brightness doesn't reflect the actual backlight level. Always invoke backlight_update_status when users want to change the backlight.

For setups where brightness change is an expensive operation,
this could be done in the driver rather than the core.

http://bugzilla.kernel.org/show_bug.cgi?id=12249

Signed-off-by: Zhang Rui <[e-mail]>
Signed-off-by: Richard Purdie <[e-mail]>

drivers/video/backlight/backlight.c

···
 		else {
 			pr_debug("backlight: set brightness to %lu\n",
 				 brightness);
-			if (bd->props.brightness != brightness) {
-				bd->props.brightness = brightness;
-				backlight_update_status(bd);
-			}
+			bd->props.brightness = brightness;
+			backlight_update_status(bd);
 			rc = count;
 		}
 	}