Fixes problem in model build with 'TIMING_SIGNAL' undefined.
Building an IOP model on X7 would fail because 'TIMING_SIGNAL' was undefined. This fixes the problem. It looks like this would only show up in IOP models.
Building an IOP model on X7 would fail because 'TIMING_SIGNAL' was undefined. This fixes the problem. It looks like this would only show up in IOP models.