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/mm/shmem.c b/mm/shmem.c
index 4c5e68e..8184342 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2261,7 +2261,7 @@
 #ifdef CONFIG_TMPFS
 	devfs_mk_dir("shm");
 #endif
-	shm_mnt = do_kern_mount(tmpfs_fs_type.name, MS_NOUSER,
+	shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
 				tmpfs_fs_type.name, NULL);
 	if (IS_ERR(shm_mnt)) {
 		error = PTR_ERR(shm_mnt);