tg3: Track LP advertising

This patch adds code to track the autonegotiation advertisements of the
link partner and report them through ethtool.

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