boards/frdm-k64f: Fix units & alignment in doc
boards/frdm-k64f: Fix units & alignment in doc

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