* nrf: Adding Arduino Primo board support * nrf: Adding arduino_primo to target boards table in readme.md * nrf/boards: Activating pyb.LED module for arduino_primo board. * nrf/boards: Removing define not needed for arduino_primo Updating arduino_primo board mpconfigboard.h. Removing a define that was wrongly named. Instead of renaming it, it was removed as it was never used.