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>
diff --git a/fs/squashfs/dir.c b/fs/squashfs/dir.c
index d8c2d74..a5845f9 100644
--- a/fs/squashfs/dir.c
+++ b/fs/squashfs/dir.c
@@ -231,6 +231,6 @@
 
 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,
 };