LEGO EV3 Color sensor RGB-RAW mode.

[dlech]

The RGB-RAW mode of the LEGO EV3 Color sensor (UART) always returns a bad checksum. The checksum should be ignored in this mode so that it can be used.

References:

• https://github.com/ev3dev/lego-linux-drivers/blob/master/sensors/ev3_uart_sensor_ld.c#L601
• Workaround to support LEGO EV3 Color Sensor in RGB-RAW mode mindboards/ev3sources#30