bnx2x: change smp_mb() comment to conform the true

Access to fp->tx_bp_prod is protected by __netif_tx_lock,
smp_mb() is not needed for that.
Signed-off-by: NStanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: NEilon Greenstein <eilong@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/bnx2x_main.c

@@ -11428,9 +11428,12 @@ static netdev_tx_t bnx2x_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	if (unlikely(bnx2x_tx_avail(fp) < MAX_SKB_FRAGS + 3)) {
 		netif_tx_stop_queue(txq);
-		/* We want bnx2x_tx_int to "see" the updated tx_bd_prod
-		   if we put Tx into XOFF state. */
+
+		/* paired memory barrier is in bnx2x_tx_int(), we have to keep
+		 * ordering of set_bit() in netif_tx_stop_queue() and read of
+		 * fp->bd_tx_cons */
 		smp_mb();
+
 		fp->eth_q_stats.driver_xoff++;
 		if (bnx2x_tx_avail(fp) >= MAX_SKB_FRAGS + 3)
 			netif_tx_wake_queue(txq);