bnx2x: PCI configuration bug on big-endian

The current code read nothing but zeros on big-endian (wrong part of the
32bits). This caused poor performance on big-endian machines. Though this
issue did not cause the system to crash, the performance is significantly
better with the fix so I view it as critical bug fix.

Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>