[TG3]: Add 5784 and 5764 support.

This patch adds the support for 5784 and 5764 devices.

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