tg3: Add unicast filtering support.

Up to 3 additional unicast addresses can be added to the perfect match
filter table.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>