[ARM] pxafb: avoid the racing condition in pxafb_smart_thread

fbi->state change shall really be protected by fbi->ctrlr_lock, where
the change is sheltered. There is a possibility that pxafb_smart_thread
will start update the LCD panel when fbi->state == C_ENABLE, while
all other initialization isn't done.
Signed-off-by: Eric Miao <eric.miao@marvell.com>

drivers/video/pxafb.c

@@ -794,11 +794,15 @@ static int pxafb_smart_thread(void *arg)
 		if (try_to_freeze())
 			continue;
 
+		mutex_lock(&fbi->ctrlr_lock);
+
 		if (fbi->state == C_ENABLE) {
 			inf->smart_update(&fbi->fb);
 			complete(&fbi->refresh_done);
 		}
 
+		mutex_unlock(&fbi->ctrlr_lock);
+
 		set_current_state(TASK_INTERRUPTIBLE);
 		schedule_timeout(30 * HZ / 1000);
 	}