SERIAL_XON_XOFF not supported on USB-native AVR devices
User could enable SERIAL_XON_XOFF on USB-native devices and it would not be enabled without warning, but M115 would report the capability as available.
[2.0.x] Enable hardware serial ports on LPC1768 (#8004)
* Enable hardware serial ports on LPC1768
* Fix compilation errors with other HALs
* FIx order of includes in LPC1768 HAL main.cpp
* Add support for RX_BUFFER_SIZE and TX_BUFFER_SIZE options in Configuration_adv.h
Includes:
*firmware version / branch / date.
*extruder count
*board information (name, serial details, power supply type)
*thermistors (names, min/max temperatures)
*printer statistics (PRINTCOUNTER details)
Thanks to @thinkyhead for contributions.