net/mlx5e: Fix failing ethtool query on FEC query error

If FEC caps query fails when executing 'ethtool <interface>'
the whole callback fails unnecessarily, fixed that by replacing the
error return code with debug logging only.

Fixes: 6cfa9460 ("net/mlx5e: Ethtool driver callback for query/set FEC policy")
Signed-off-by: Shay Agroskin <shayag@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c

@@ -843,8 +843,7 @@ static int mlx5e_get_link_ksettings(struct net_device *netdev,
 	ethtool_link_ksettings_add_link_mode(link_ksettings, supported,
 					     Autoneg);
 
-	err = get_fec_supported_advertised(mdev, link_ksettings);
-	if (err)
+	if (get_fec_supported_advertised(mdev, link_ksettings))
 		netdev_dbg(netdev, "%s: FEC caps query failed: %d\n",
 			   __func__, err);