can: raw: process optimization in raw_init()

Now, register notifier after register proto successfully. It can create
raw socket and set socket options once register proto successfully, so it
is possible missing notifier event before register notifier successfully
although this is a low probability scenario.

Move notifier registration to the front of proto registration like done
in j1939. In addition, register_netdevice_notifier() may fail, check its
result is necessary.

Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Link: https://lore.kernel.org/all/7af9401f0d2d9fed36c1667b5ac9b8df8f8b87ee.1661584485.git.william.xuanziyang@huawei.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/raw.c

@@ -942,12 +942,20 @@ static __init int raw_module_init(void)
 
 	pr_info("can: raw protocol\n");
 
-	err = can_proto_register(&raw_can_proto);
-	if (err < 0)
-		pr_err("can: registration of raw protocol failed\n");
-	else
-		register_netdevice_notifier(&canraw_notifier);
+	err = register_netdevice_notifier(&canraw_notifier);
+	if (err)
+		return err;
 
+	err = can_proto_register(&raw_can_proto);
+	if (err < 0) {
+		pr_err("can: registration of raw protocol failed\n");
+		goto register_proto_failed;
+	}
+
+	return 0;
+
+register_proto_failed:
+	unregister_netdevice_notifier(&canraw_notifier);
 	return err;
 }