net: bridge: Issue NETDEV_PRE_CHANGEADDR

When a port is attached to a bridge, the address of the bridge in
question may change as well. Even if it would not change at this
point (because the current bridge address is lower), it might end up
changing later as a result of detach of another port, which can't be
vetoed.

Therefore issue NETDEV_PRE_CHANGEADDR regardless of whether the address
will be used at this point or not, and make sure all involved parties
would agree with the change.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>