Add I2C Controller brownout mitigations

[ChrisChrisLoLo]

When you add on a module to the controller hotswap style (controller is powered on), it has a tendency to shut down, if only for a brief period of time.

I suspect the cause is some sort of brownout, where the peripheral drains too much current from the controller too quickly.

The easiest first thing to try might be to add a reservoir capacitor. I'm not sure what the capacitance should generally be, and I'm not even sure if it will help or not