kernfs: kernfs_sop_show_path: don't return 0 after seq_dentry call

BugLink: http://bugs.launchpad.net/bugs/1584163

Our caller expects 0 on success, not >0.

This fixes a bug in the patch

	cgroup, kernfs: make mountinfo show properly scoped path for cgroup namespaces

where /sys does not show up in mountinfo, breaking criu.

Thanks for catching this, Andrei.
Reported-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
(cherry picked from commit 3cc9b23c)
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

fs/kernfs/mount.c

@@ -50,7 +50,8 @@ static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
 	if (scops && scops->show_path)
 		return scops->show_path(sf, node, root);
 
-	return seq_dentry(sf, dentry, " \t\n\\");
+	seq_dentry(sf, dentry, " \t\n\\");
+	return 0;
 }
 
 const struct super_operations kernfs_sops = {