bridge: Update outdated comment on promiscuous mode

Now bridge ports can be non-promiscuous, vlan_vid_add() is no longer an
unnecessary operation.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed