AIN signal to DAC output mapping inconsistent between brake, throttle and steering modules

[jonlamb-gh]

All of the modules should have a consistent mapping between the analog input hight/low signals and the DAC output A/B channels.

I think the mapping should be:

• AIN signal high maps to DAC channel A
• AIN signal low maps to DAC channel B

Currently the brake and throttle modules are inverting the mapping when they
call the prevent_signal_discontinuity() function.

The steering module seems to be using them correctly.

TODO Confirm this is a bug in the OSCC firmware or just a hardware pin mapping issue.

Can we do away with high/low and just have A/B for both input and output?

[jonlamb-gh]

Some discussion in these:

• PolySync/oscc@99b4f17
• Fix swapped voltages PolySync/oscc#244
• Remove check for controller command timeouts PolySync/oscc#217