bnx2x: Fix link issue with DAC over 578xx

Fix no-link issue on BCM578xx when direct attached cable is connected since Warpcore microcode restart was missing to re-read the new mode.

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>