bnx2: Fix endian swapping on firmware version string

so that ethtool -i will display it correctly on big endian systems.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Reviewed-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>