boards/esp_common: fix refs to CPU doc section
boards/esp_common: fix refs to CPU doc section


RIOT-OS/RIOT,jasonatran/RIOT,ant9000/RIOT,ant9000/RIOT,jasonatran/RIOT,jasonatran/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kYc0o/RIOT,ant9000/RIOT,kaspar030/RIOT,miri64/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,ant9000/RIOT,ant9000/RIOT,kaspar030/RIOT,kYc0o/RIOT,miri64/RIOT,OlegHahm/RIOT,miri64/RIOT,kaspar030/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,miri64/RIOT,kYc0o/RIOT,kYc0o/RIOT,OlegHahm/RIOT,miri64/RIOT,kaspar030/RIOT,OlegHahm/RIOT