Remove domXcvr functions.

Until now, they are a convoluted way of saying "0" or "1". Also, for some reason it sets a register, but reads the values set from program memory instead of hardware. On the original driver, domXcvr is set to 0 on the constructor and then never changed.

For some reason, here it was being called inside the tearDownRing function. Changed that to be set on the constructor.