Fix bus response submessage within I2CDeviceInitResponse

[brentru]

• Changes the bus response within I2cDeviceInitResponse from I2CBusInitResponse to expected BusResponse, matching the sub-message within I2CBusScanResponse.
• Adds bus_response field to I2CDeviceUpdateResponse as the device could hang during I2C transactions here.

[brentru]

ping @lorennorman

[brentru]

@lorennorman Changed from response to bus_response in https://github.com/adafruit/Wippersnapper_Protobuf/pull/77/commits/868626af7332b9e27a35e60f853715173739cf6e, thanks for the catch.