gnrc_tcp: Fix typo in config.h
gnrc_tcp: Fix typo in config.h

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