romfs, squashfs: switch to ->iterate_shared()

don't need to lock directory in ->llseek(), either

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

fs/squashfs/dir.c

@@ -231,6 +231,6 @@ failed_read:
 
 const struct file_operations squashfs_dir_ops = {
 	.read = generic_read_dir,
-	.iterate = squashfs_readdir,
-	.llseek = default_llseek,
+	.iterate_shared = squashfs_readdir,
+	.llseek = generic_file_llseek,
 };