net: cleanup init_dummy_netdev_core()

init_dummy_netdev_core() used to cater to net_devices which
did not come from alloc_netdev_mqs(). Since that's no longer
supported remove the init logic which duplicates alloc_netdev_mqs().

While at it rename back to init_dummy_netdev().

Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20250113003456.3904110-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -10736,26 +10736,20 @@ int register_netdevice(struct net_device *dev)
 EXPORT_SYMBOL(register_netdevice);
 
 /* Initialize the core of a dummy net device.
- * This is useful if you are calling this function after alloc_netdev(),
- * since it does not memset the net_device fields.
+ * The setup steps dummy netdevs need which normal netdevs get by going
+ * through register_netdevice().
  */
-static void init_dummy_netdev_core(struct net_device *dev)
+static void init_dummy_netdev(struct net_device *dev)
 {
 	/* make sure we BUG if trying to hit standard
 	 * register/unregister code path
 	 */
 	dev->reg_state = NETREG_DUMMY;
 
-	/* NAPI wants this */
-	INIT_LIST_HEAD(&dev->napi_list);
-
 	/* a dummy interface is started by default */
 	set_bit(__LINK_STATE_PRESENT, &dev->state);
 	set_bit(__LINK_STATE_START, &dev->state);
 
-	/* napi_busy_loop stats accounting wants this */
-	dev_net_set(dev, &init_net);
-
 	/* Note : We dont allocate pcpu_refcnt for dummy devices,
 	 * because users of this 'device' dont need to change
 	 * its refcount.
@@ -11440,7 +11434,7 @@ EXPORT_SYMBOL(free_netdev);
 struct net_device *alloc_netdev_dummy(int sizeof_priv)
 {
 	return alloc_netdev(sizeof_priv, "dummy#", NET_NAME_UNKNOWN,
-			    init_dummy_netdev_core);
+			    init_dummy_netdev);
 }
 EXPORT_SYMBOL_GPL(alloc_netdev_dummy);