p54usb: fix random traffic stalls (LM87)

All LM87 firmwares need a explicit termination "packet",
in oder to finish the pending transfer properly.
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/p54usb.c

@@ -285,6 +285,7 @@ static void p54u_tx_lm87(struct ieee80211_hw *dev, struct sk_buff *skb)
 	usb_fill_bulk_urb(data_urb, priv->udev,
 			  usb_sndbulkpipe(priv->udev, P54U_PIPE_DATA),
 			  skb->data, skb->len, p54u_tx_cb, skb);
+	data_urb->transfer_flags |= URB_ZERO_PACKET;
 
 	usb_anchor_urb(data_urb, &priv->submitted);
 	if (usb_submit_urb(data_urb, GFP_ATOMIC)) {