nfc: Fix RC-S380* needs zero-length packet

If sent packet size is wMaxPacketSize boundary, this device doesn't
answer. To fix this, we have to send zero-length packet in usb spec.
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/port100.c

@@ -1540,6 +1540,7 @@ static int port100_probe(struct usb_interface *interface,
 	usb_fill_bulk_urb(dev->out_urb, dev->udev,
 			  usb_sndbulkpipe(dev->udev, out_endpoint),
 			  NULL, 0, port100_send_complete, dev);
+	dev->out_urb->transfer_flags = URB_ZERO_PACKET;
 
 	dev->skb_headroom = PORT100_FRAME_HEADER_LEN +
 			    PORT100_COMM_RF_HEAD_MAX_LEN;