net/mlx5e: Fix error path for ethtool set-priv-flag

Expose error value when failing to comply to command:
$ ethtool --set-priv-flags eth2 rx_cqe_compress [on/off]

Fixes: be7e87f ("net/mlx5e: Fail safe cqe compressing/moderation mode setting")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -1887,6 +1887,7 @@ static int set_pflag_rx_cqe_compress(struct net_device *netdev,
 {
 	struct mlx5e_priv *priv = netdev_priv(netdev);
 	struct mlx5_core_dev *mdev = priv->mdev;
+	int err;
 
 	if (!MLX5_CAP_GEN(mdev, cqe_compression))
 		return -EOPNOTSUPP;
@@ -1896,7 +1897,10 @@ static int set_pflag_rx_cqe_compress(struct net_device *netdev,
 		return -EINVAL;
 	}
 
-	mlx5e_modify_rx_cqe_compression_locked(priv, enable);
+	err = mlx5e_modify_rx_cqe_compression_locked(priv, enable);
+	if (err)
+		return err;
+
 	priv->channels.params.rx_cqe_compress_def = enable;
 
 	return 0;