Revert "Don't let DSM input corrupt PX4IO memory"

This reverts commit aa90c24a81d784cba6fa1ab3b28678d897d099fd.
PX4IO_CONTROL_CHANNELS and PX4IO_INPUT_CHANNELS redundant

PX4IO_CONTROL_CHANNELS and PX4IO_INPUT_CHANNELS #defines both mean the
same thing. Use one and delete the other to avoid errors.