net/mlx4_en: Save slave ethtool stats command

Following the previous patch, as an optimization, the slave will
not even bother sending the DUMP_ETH_STATS command over the
comm channel.
Signed-off-by: NTariq Toukan <tariqt@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/en_netdev.c

@@ -1917,6 +1917,7 @@ static void mlx4_en_clear_stats(struct net_device *dev)
 	struct mlx4_en_dev *mdev = priv->mdev;
 	int i;
 
+	if (!mlx4_is_slave(mdev->dev))
 		if (mlx4_en_DUMP_ETH_STATS(mdev, priv->port, 1))
 			en_dbg(HW, priv, "Failed dumping statistics\n");