usbnet: ipheth: do not stop RX on failing RX callback

RX callbacks can fail for multiple reasons:

* Payload too short
* Payload formatted incorrecly (e.g. bad NCM framing)
* Lack of memory

None of these should cause the driver to seize up.

Make such failures non-critical and continue processing further
incoming URBs.
Signed-off-by: Foster Snowhill <forst@pen.gy>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/ipheth.c

@@ -308,7 +308,6 @@ static void ipheth_rcvbulk_callback(struct urb *urb)
 	if (retval != 0) {
 		dev_err(&dev->intf->dev, "%s: callback retval: %d\n",
 			__func__, retval);
-		return;
 	}
 
 rx_submit: