rtnetlink: bring NETDEV_CHANGELOWERSTATE event process back to rtnetlink_event

This patch is to bring NETDEV_CHANGELOWERSTATE event process back
to rtnetlink_event so that bonding could use it instead of calling
rtmsg_ifinfo to send a notification to userspace after netdev lower
state is changed in the later patch.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -4385,6 +4385,7 @@ static int rtnetlink_event(struct notifier_block *this, unsigned long event, voi
 	case NETDEV_CHANGEUPPER:
 	case NETDEV_RESEND_IGMP:
 	case NETDEV_CHANGEINFODATA:
+	case NETDEV_CHANGELOWERSTATE:
 	case NETDEV_CHANGE_TX_QUEUE_LEN:
 		rtmsg_ifinfo_event(RTM_NEWLINK, dev, 0, rtnl_get_event(event),
 				   GFP_KERNEL, NULL);