bnx2x: Add and correct PCI link speed prints

This adds the print of the PCI gen3 link speed (8GHz), as well as correcting
the same print for 57712 boards (the print erroneously showed a 2.5GHz speed).

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