bnx2x: Remove 100Mb force speed for BCM84833

Remove unsupported speed of 100Mb force for BCM84833 due to hardware
limitation.

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>