bnx2x: Fix port identification for the 84834

Fix the "ethtool -p" for boards with BCM84834, by using LED4 of the PHY
to toggle the link LED while keeping interrupt disabled to avoid NIG attentions,
and at the end restore NIG to previous state.

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>