mlx4: Return EOPNOTSUPP instead of ENOTSUPP

In commit b45f0674b997 ("mlx4: xdp: Allow raising MTU up to one page minus eth and vlan hdrs"),
it changed EOPNOTSUPP to ENOTSUPP by mistake.  This patch fixes it.

Fixes: b45f0674b997 ("mlx4: xdp: Allow raising MTU up to one page minus eth and vlan hdrs")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -2277,7 +2277,7 @@ static int mlx4_en_change_mtu(struct net_device *dev, int new_mtu)
 
 	if (priv->tx_ring_num[TX_XDP] &&
 	    !mlx4_en_check_xdp_mtu(dev, new_mtu))
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 
 	dev->mtu = new_mtu;