usbnet: fix leak of transfer buffer of dev->interrupt

The transfer buffer of dev->interrupt is allocated in .probe path,
but not freed in .disconnet path, so mark the interrupt URB as
URB_FREE_BUFFER to free the buffer when the URB is destroyed.
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c

@@ -210,6 +210,7 @@ static int init_status (struct usbnet *dev, struct usb_interface *intf)
 		} else {
 			usb_fill_int_urb(dev->interrupt, dev->udev, pipe,
 				buf, maxp, intr_complete, dev, period);
+			dev->interrupt->transfer_flags |= URB_FREE_BUFFER;
 			dev_dbg(&intf->dev,
 				"status ep%din, %d bytes period %d\n",
 				usb_pipeendpoint(pipe), maxp, period);