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/afs/super.h b/fs/afs/super.h
index ac11362..32de8cc 100644
--- a/fs/afs/super.h
+++ b/fs/afs/super.h
@@ -38,6 +38,8 @@
 	return sb->s_fs_info;
 }
 
+extern struct file_system_type afs_fs_type;
+
 #endif /* __KERNEL__ */
 
 #endif /* _LINUX_AFS_SUPER_H */