gnrc/ndp: bugfix set O-flag on non anycast target
gnrc/ndp: bugfix set O-flag on non anycast target

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