bnx2x: half duplex support added for several boards

From: Yaniv Rosner <yaniv.rosner@broadcom.com>

Several boards require an additional HW bit written in-order to enable
half duplex.

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