Bridge port attributes are offloaded to hardware when invoked with SELF
flag set, but it really makes no sense to reflect them when port is not
bridged.

Allow a user to change these attribute only when port is bridged and
initialize them correctly when joining or leaving a bridge.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>