sysfs: fix sysfs lockdep warning in mlx4 code

This fixes a sysfs lockdep warning in the mlx4 code.

Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/net/mlx4/main.c

@@ -1023,6 +1023,7 @@ static int mlx4_init_port_info(struct mlx4_dev *dev, int port)
 	info->port_attr.attr.mode = S_IRUGO | S_IWUSR;
 	info->port_attr.show      = show_port_type;
 	info->port_attr.store     = set_port_type;
+	sysfs_attr_init(&info->port_attr.attr);
 
 	err = device_create_file(&dev->pdev->dev, &info->port_attr);
 	if (err) {