bnx2x: fix 57840_MF pci id

Commit c3def943 have added support for
new pci ids of the 57840 board, while failing to change the obsolete value
in 'pci_ids.h'.
This patch does so, allowing the probe of such devices.

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>