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/romfs/super.c b/fs/romfs/super.c
index 6b00ca3..d0f8a38 100644
--- a/fs/romfs/super.c
+++ b/fs/romfs/super.c
@@ -280,8 +280,8 @@
 
 static const struct file_operations romfs_dir_operations = {
 	.read		= generic_read_dir,
-	.iterate	= romfs_readdir,
-	.llseek		= default_llseek,
+	.iterate_shared	= romfs_readdir,
+	.llseek		= generic_file_llseek,
 };
 
 static const struct inode_operations romfs_dir_inode_operations = {