bnx2x: Prevent "Unknown MF" print in SF mode

When using a chip operating in Single Function mode, when the chip is probed
the bnx2x would print a message warning of an unknown Multi Function mode.

This patch prevents said message.

Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>