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: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index b35366c..ea81a05 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -729,8 +729,8 @@
 
 	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;
 }