microcom: Fix various review comments
microcom: Fix various review comments

 - Expand the description to prevent confusion
 - Use 'baud rate' instead of baudrate
 - Replace '-' chars in example parameter values with '_'
 - Remove the telnet RFC number

slash3b/tldr,felixonmars/tldr,slash3b/tldr,felixonmars/tldr,felixonmars/tldr,slash3b/tldr