backlight: Show brightness even if get_brightness is not implemented

Many implementations of get_brightness operation returns only value
of props.brightness field. This change makes such implementations
unnecessary.
Acked-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NAndrzej Hajda <a.hajda@samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/video/backlight/backlight.c

@@ -223,6 +223,8 @@ static ssize_t actual_brightness_show(struct device *dev,
 	mutex_lock(&bd->ops_lock);
 	if (bd->ops && bd->ops->get_brightness)
 		rc = sprintf(buf, "%d\n", bd->ops->get_brightness(bd));
+	else
+		rc = sprintf(buf, "%d\n", bd->props.brightness);
 	mutex_unlock(&bd->ops_lock);
 
 	return rc;