[BRIDGE]: receive link-local on disabled ports.

This change allows link local packets (like 802.3ad and Spanning Tree
Protocol) to be processed even when the bridge is not using the port.
It fixes the chicken-egg problem for bridging a bonded device, and
may also fix problems with spanning tree failover.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>