convert xenfs

entirely static tree, populated by simple_fill_super().  Can switch
to kill_anon_super() without any other changes.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/xen/xenfs/super.c

@@ -88,7 +88,7 @@ static struct file_system_type xenfs_type = {
 	.owner =	THIS_MODULE,
 	.name =		"xenfs",
 	.init_fs_context = xenfs_init_fs_context,
-	.kill_sb =	kill_litter_super,
+	.kill_sb =	kill_anon_super,
 };
 MODULE_ALIAS_FS("xenfs");