Btrfs: sysfs: add support to add parent for fsid

To support seed sysfs layout and represent seed fsid under
the sprout we need the facility to create fsid under the
specified parent.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.cz>

fs/btrfs/sysfs.c

@@ -729,8 +729,8 @@ int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs,
 
 	init_completion(&fs_devs->kobj_unregister);
 	fs_devs->super_kobj.kset = btrfs_kset;
-	error = kobject_init_and_add(&fs_devs->super_kobj, &btrfs_ktype, NULL,
-				     "%pU", fs_devs->fsid);
+	error = kobject_init_and_add(&fs_devs->super_kobj,
+				&btrfs_ktype, parent, "%pU", fs_devs->fsid);
 	return error;
 }