Trailing parentheses when undefining a macro
lead to compiler 'extra token' warnings
Inspired by - https://forums.freertos.org/t/avr-gcc-warning-extra-tokens-at-end-of-undef-in-porthardware-h/16365/4
- Update AVR GCC port files (now the port.c and portmacro.h files are
identical for AVR_Mega0 and AVR_Dx families).
- Add support for low-power tickless mode in portable files for AVR_Dx and
AVR_Mega0.
This change was originally contributed by alexmchp@ in the following PR:
https://github.com/FreeRTOS/FreeRTOS-Kernel/pull/373