usb: USB storage-specific part ifdef in uclass

usb_stor_reset is only defined when USB storage support is enabled, thus the
function is not declared when such support is missing.
Signed-off-by: NPaul Kocialkowski <contact@paulk.fr>

drivers/usb/host/usb-uclass.c

@@ -173,7 +173,9 @@ int usb_stop(void)
 	uclass_foreach_dev(dev, uc)
 		usb_emul_reset(dev);
 #endif
+#ifdef CONFIG_USB_STORAGE
 	usb_stor_reset();
+#endif
 	usb_hub_reset();
 	uc_priv->companion_device_count = 0;
 	usb_started = 0;