+
+static int __devexit ipmi_of_remove(struct of_device *dev)
+{
+	/* should call
+	 * cleanup_one_si(dev->dev.driver_data); */
+	return 0;
+}

If your remove doesn't work, don't implement one. Though since you don't
have the choice in having a module_exit or not, you should really
implement one that works :-)

Ben.