net/mlx4_core: Fix error handling in mlx4_init_port_info.

Avoid exiting the function with a lingering sysfs file (if the first
call to device_create_file() fails while the second succeeds), and avoid
calling devlink_port_unregister() twice.

In other words, either mlx4_init_port_info() succeeds and returns zero, or
it fails, returns non-zero, and requires no cleanup.

Fixes: 096335b ("mlx4_core: Allow dynamic MTU configuration for IB ports")
Signed-off-by: Tarick Bedeir <tarick@google.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -2929,6 +2929,7 @@ static int mlx4_init_port_info(struct mlx4_dev *dev, int port)
 		mlx4_err(dev, "Failed to create file for port %d\n", port);
 		devlink_port_unregister(&info->devlink_port);
 		info->port = -1;
+		return err;
 	}
 
 	sprintf(info->dev_mtu_name, "mlx4_port%d_mtu", port);
@@ -2950,9 +2951,10 @@ static int mlx4_init_port_info(struct mlx4_dev *dev, int port)
 				   &info->port_attr);
 		devlink_port_unregister(&info->devlink_port);
 		info->port = -1;
+		return err;
 	}
 
-	return err;
+	return 0;
 }
 
 static void mlx4_cleanup_port_info(struct mlx4_port_info *info)