VFS: Unexport do_kern_mount() and clean up simple_pin_fs()

Replace all module uses with the new vfs_kern_mount() interface, and fix up
simple_pin_fs().

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index b55b4ea..90f9417 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -199,7 +199,7 @@
 
 	pr_debug("debugfs: creating file '%s'\n",name);
 
-	error = simple_pin_fs("debugfs", &debugfs_mount, &debugfs_mount_count);
+	error = simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
 	if (error)
 		goto exit;