platform/x86: ibm_rtl: move to use bus_get_dev_root()

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Mark Gross <markgross@kernel.org>
Cc: platform-driver-x86@vger.kernel.org
Acked-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230313182918.1312597-4-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/platform/x86/ibm_rtl.c

@@ -199,16 +199,26 @@ static int rtl_setup_sysfs(void) {
 
 	ret = subsys_system_register(&rtl_subsys, NULL);
 	if (!ret) {
+		struct device *dev_root = bus_get_dev_root(&rtl_subsys);
+
+		if (dev_root) {
 			for (i = 0; rtl_attributes[i]; i ++)
-			device_create_file(rtl_subsys.dev_root, rtl_attributes[i]);
+				device_create_file(dev_root, rtl_attributes[i]);
+			put_device(dev_root);
+		}
 	}
 	return ret;
 }
 
 static void rtl_teardown_sysfs(void) {
+	struct device *dev_root = bus_get_dev_root(&rtl_subsys);
 	int i;
+
+	if (dev_root) {
 		for (i = 0; rtl_attributes[i]; i ++)
-		device_remove_file(rtl_subsys.dev_root, rtl_attributes[i]);
+			device_remove_file(dev_root, rtl_attributes[i]);
+		put_device(dev_root);
+	}
 	bus_unregister(&rtl_subsys);
 }