atm: [br2684] allow routed mode operation again

in routed mode, we don't have a hardware address so netdev_ops doesnt
need to validate our hardware address via .ndo_validate_addr

Reported-by: Manuel Fuentes <mfuentes@agenciaefe.com>
Signed-off-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Signed-off-by: David S. Miller <davem@davemloft.net>