sim: iq2000: drop unused cpu define logic

sim: iq2000: drop unused cpu define logic

These defines seem to have been added in anticipation of adding another
cpu port (IQ10BF?), but that was over 20 years ago, and that port has
yet to materialize.  So drop these compile flags since they don't do
anything to the generated code.  If another port ever shows up, it's
easy enough to readd things as needed.