testsuite: use right offset for module name

testsuite: use right offset for module name

We need to cope with the case in which a 32 bits machine is opening a 64
bits kernel module and vice-versa. The offset in `struct module' are
different and do not depend on the architecture we are running, but
rather on the architecture they were created for.

This fixes `make check' in 32 bits machines (since we are shipping 64
bits modules for testing)