usbip: vhci_hcd: at unlink, return -EIDRM if vhci_rx took the urb

In a situation where the urb is about to be returned or was never
there, we should return -EIDRM (as per usb_hcd_check_unlink_urb).
This is exactly the situation when the urb is picked up by vhci_rx
before we access priv.

Return -EIDRM rather than 0 when this happens.
Signed-off-by: NIgor Kotrasinski <i.kotrasinsk@samsung.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/usbip/vhci_hcd.c

@@ -631,7 +631,7 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
 		/* URB was never linked! or will be soon given back by
 		 * vhci_rx. */
 		spin_unlock(&the_controller->lock);
-		return 0;
+		return -EIDRM;
 	}
 
 	{