rk_pinctrl: Only add gpio subnode

This is the only node we are interested in so do not waste time to test
creating device that will be either unused or fail as most of the nodes
don't have a compatible string.

sys/arm64/rockchip/rk_pinctrl.c

@@ -438,6 +438,8 @@ rk_pinctrl_attach(device_t dev)
 
 	/* Attach child devices */
 	for (node = OF_child(node); node > 0; node = OF_peer(node)) {
+		if (!ofw_bus_node_is_compatible(node, "rockchip,gpio-bank"))
+			continue;
 		cdev = simplebus_add_device(dev, node, 0, NULL, -1, NULL);
 		if (cdev != NULL)
 			device_probe_and_attach(cdev);