bnx2x: Fix incorrect link-up report

Fix a problem where link is reported to be up when SFP+ module is plugged in
without cable. This occurs with specific module types which may generate
temporary TX_FAULT indication. Solution is to avoid changing any link parameters
when checking TX_FAULT indication while physical link is down.

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>