bnx2x: Fix false link indication at link partner when DAC is used

When driver is unloaded, disable PMD in addition to TX laser, provided that the management firmware will be able to enable it back.

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>