bnx2x: Adding XAUI CL73 autoneg support

Adding CL73 support to the built in PHY in the 5771x device. Also supporting
fallbacks to CL73 if the link partner does not respond.

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>