bnx2x: revised and corrected SPIO access

Changed naming convention of SPIO macros, and prevented access to invalid SPIOs.

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>