Disable clock stretching on Pi I2C bus

[Lohrer]

The Raspberry Pi doesn't properly support clock stretching, see https://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html. This can caused data to be read/written improperly to the Preamp Board's micro. The micro can disable clock stretching, but we have to have data ready for any potential read. Investigate if we can fully disable clock stretching.