bonding: remove rtmsg_ifinfo called in bond_master_upper_dev_link

Since commit 42e52bf9 ("net: add netnotifier event for upper device
change"), netdev_master_upper_dev_link has generated NETDEV_CHANGEUPPER
event which would send a notification to userspace in rtnetlink_event.

There's no need to call rtmsg_ifinfo to send the notification any more.
So this patch is to remove it from bond_master_upper_dev_link as well
as bond_upper_dev_unlink to avoid the redundant notifications.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>