In one of the previous changes for dual-rate a wrong value for the
sysref divider made it into test_two_sample_rates. This fixes this and
makes the MPM tests green again.
This new test checks that the configurations in the X440 dual rate case
are inverted if the master clock rates are inverted and not changed. We
used to see different configurations per daughterboard when swapping the
MCRs which was fixed with the previous commit. This test ensures that
with future changes we don't break this again.
