Took it out as it was only used in one place now (here.) The reason for moving to integer voltages was we have some new boards coming out with different power supply models, and didn't want to have to keep bleeding the implementation details into the miner firmware.

However that's no real need to remove the enum entirely, and in doing so I introduced a subtle bug (750mV and 850mV settings are swapped.) Reintroduced in 83b166d.