file_operations: get back C89 compatible initializer

Signed-off-by: Petro Karashchenko <petro.karashchenko@gmail.com>

drivers/net/tun.c

@@ -237,9 +237,9 @@ static const struct file_operations g_tun_file_ops =
   tun_write,    /* write */
   NULL,         /* seek */
   tun_ioctl,    /* ioctl */
-  tun_poll,     /* poll */
+  tun_poll      /* poll */
 #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
-  NULL,         /* unlink */
+  , NULL        /* unlink */
 #endif
 };