/net/sock/udp: designated iolist_t intializer
/net/sock/udp: designated iolist_t intializer

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