usb: return error code instead of 0 in the enqueue function.

if the enqueue function returns -ESHUTDOWN or -ENOMEM then
we return 0 instead of an error. This leads to a timeout and
then to a dequeue request of an not enqueued urb.
Signed-off-by: Sebastian Siewior <sebastian@breakpoint.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/isp1760-hcd.c

@@ -1615,8 +1615,7 @@ static int isp1760_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,
 		return -EPIPE;
 	}
 
-	isp1760_prepare_enqueue(priv, urb, &qtd_list, mem_flags, pe);
-	return 0;
+	return isp1760_prepare_enqueue(priv, urb, &qtd_list, mem_flags, pe);
 }
 
 static int isp1760_urb_dequeue(struct usb_hcd *hcd, struct urb *urb,