boards/openmote-cc2538: fix broken links
boards/openmote-cc2538: fix broken links

yogo1212/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,OlegHahm/RIOT,miri64/RIOT,authmillenon/RIOT,authmillenon/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,authmillenon/RIOT,kYc0o/RIOT,jasonatran/RIOT,miri64/RIOT,jasonatran/RIOT,ant9000/RIOT,authmillenon/RIOT,basilfx/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,kYc0o/RIOT,basilfx/RIOT,OTAkeys/RIOT,authmillenon/RIOT,ant9000/RIOT,kaspar030/RIOT,OlegHahm/RIOT,ant9000/RIOT,miri64/RIOT,jasonatran/RIOT,basilfx/RIOT,OTAkeys/RIOT,ant9000/RIOT,kaspar030/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,ant9000/RIOT,yogo1212/RIOT,authmillenon/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,kYc0o/RIOT,yogo1212/RIOT,basilfx/RIOT,yogo1212/RIOT,jasonatran/RIOT,kaspar030/RIOT,miri64/RIOT,kaspar030/RIOT,yogo1212/RIOT,basilfx/RIOT,miri64/RIOT,kYc0o/RIOT