bnx2x: NULL dereference on error in debug code

"vfop" is NULL here.  I've changed the debugging to not use it.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Ariel Elior <ariele@broadcom.com>
Acked-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>