NET: nps_enet: TX done acknowledge.

This is needed for when TX done interrupt is in
"level mode".
For example it is true for some simulators of this device.
Signed-off-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ezchip/nps_enet.c

@@ -150,6 +150,9 @@ static void nps_enet_tx_handler(struct net_device *ndev)
 	if (!priv->tx_packet_sent || tx_ctrl.ct)
 		return;
 
+	/* Ack Tx ctrl register */
+	nps_enet_reg_set(priv, NPS_ENET_REG_TX_CTL, 0);
+
 	/* Check Tx transmit error */
 	if (unlikely(tx_ctrl.et)) {
 		ndev->stats.tx_errors++;