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>
The existing periph_uart test depends on having more than one UART.
This test allows for manual testing with the use of a probe
on-behalf-of: @sparkmeter <ben.postman@sparkmeter.io>