leds-lp8788: forgotten unlock at lp8788_led_work

at default case of switch we return with out unlocking the mutex.
Signed-off-by: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>

drivers/leds/leds-lp8788.c

@@ -104,6 +104,7 @@ static void lp8788_led_work(struct work_struct *work)
 		lp8788_write_byte(led->lp, lp8788_pwm_addr[num], val);
 		break;
 	default:
+		mutex_unlock(&led->lock);
 		return;
 	}