netxen: bridged mode optimizations

When the interface is put in bridged mode, destination mac
addresses are unknown to firmware. So packets take a slow
path (lower priority) in firmware reducing performance.

Firmware can cache limited number of remote unicast mac
addresses for certain interval, if "dynamic mac learning"
mode is enabled.

Driver needs to enable this "mac learning" mode in firmware.
Currently this is done through net device class sysfs entry,
possibly this can also be done upon netlink notifications to
from bridge.

Signed-off-by: Narender Kumar <narender.kumar@qlogic.com>
Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>