net: inline rollback_registered_many()

Similar to the change for rollback_registered() -
rollback_registered_many() was a part of unregister_netdevice_many()
minus the net_set_todo(), which is no longer needed.

Functionally this patch moves the list_empty() check back after:

	BUG_ON(dev_boot_phase);
	ASSERT_RTNL();

but I can't find any reason why that would be an issue.
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -5709,7 +5709,7 @@ static void flush_all_backlogs(void)
 	}
 
 	/* we can have in flight packet[s] on the cpus we are not flushing,
-	 * synchronize_net() in rollback_registered_many() will take care of
+	 * synchronize_net() in unregister_netdevice_many() will take care of
 	 * them
 	 */
 	for_each_cpu(cpu, &flush_cpus)
@@ -10610,8 +10610,6 @@ void synchronize_net(void)
 }
 EXPORT_SYMBOL(synchronize_net);
 
-static void rollback_registered_many(struct list_head *head);
-
 /**
  *	unregister_netdevice_queue - remove device from the kernel
  *	@dev: device
@@ -10635,8 +10633,7 @@ void unregister_netdevice_queue(struct net_device *dev, struct list_head *head)
 		LIST_HEAD(single);
 
 		list_add(&dev->unreg_list, &single);
-		rollback_registered_many(&single);
-		list_del(&single);
+		unregister_netdevice_many(&single);
 	}
 }
 EXPORT_SYMBOL(unregister_netdevice_queue);
@@ -10649,15 +10646,6 @@ EXPORT_SYMBOL(unregister_netdevice_queue);
  *  we force a list_del() to make sure stack wont be corrupted later.
  */
 void unregister_netdevice_many(struct list_head *head)
-{
-	if (!list_empty(head)) {
-		rollback_registered_many(head);
-		list_del(head);
-	}
-}
-EXPORT_SYMBOL(unregister_netdevice_many);
-
-static void rollback_registered_many(struct list_head *head)
 {
 	struct net_device *dev, *tmp;
 	LIST_HEAD(close_head);
@@ -10665,6 +10653,9 @@ static void rollback_registered_many(struct list_head *head)
 	BUG_ON(dev_boot_phase);
 	ASSERT_RTNL();
 
+	if (list_empty(head))
+		return;
+
 	list_for_each_entry_safe(dev, tmp, head, unreg_list) {
 		/* Some devices call without registering
 		 * for initialization unwind. Remove those
@@ -10748,7 +10739,10 @@ static void rollback_registered_many(struct list_head *head)
 		dev_put(dev);
 		net_set_todo(dev);
 	}
+
+	list_del(head);
 }
+EXPORT_SYMBOL(unregister_netdevice_many);
 
 /**
  *	unregister_netdev - remove device from the kernel