Allow new ics_xcu_fpga code to run with old ADC boards.

The last tag on ics_xcu_fpga was for the old ADC boards. Since then INSTRM-616 with most of the development for the new ADC boards has been merged, and we want to run with that code.

The intent was to switch old to new hardware everywhere and never look back. Sadly, we will be running with the old ADC boards for a while, and we need to make the code run with both.

The main issues come from the polarity switch on the IR clock. This affects the clocking tables, which I unfortunately implemented in terms of the signal and not the logic. It also affects the FEE initialization, where the old card has a special clocking sequence on power up in order not to fry some part in the integrator circuit.

The other problem is with the FPGA image. I'm pretty sure that the new image will work with the old ADC cards, but need to check.