tg3: Add 5719 and 5720 to EEE_CAP list

This patch adds the 5719 and the 5720 to the list of devices that are
EEE capable.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>