Add ATmega328P Xplained Mini board. The board is an official
development kit from MCHP based on the Arduino UNO, reduced
hardware, with a xplainedmini debugger and CDC ACM serial
converter.
Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
functional changes:
- enable test to test the driver in SPI mode
style changes and code simplification:
- enable SPI mode
- fixed typos in doxygen
- fixed line length issues
- simplified code
- use fmt for formatting numbers
- use US_PER_SEC instead of magic value
- use named return values provided by driver
- use puts where ever applicable
