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: Jingoo Han <[e-mail]>
Signed-off-by: Andrzej Hajda <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/video/backlight/backlight.c

···
 	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;