backlight: wm831x_bl: Add blank line after declarations

Fixed the following checkpatch warning.

  WARNING: Missing a blank line after declarations
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/video/backlight/wm831x_bl.c

@@ -111,6 +111,7 @@ static int wm831x_backlight_update_status(struct backlight_device *bl)
 static int wm831x_backlight_get_brightness(struct backlight_device *bl)
 {
 	struct wm831x_backlight_data *data = bl_get_data(bl);
+
 	return data->current_brightness;
 }