gnrc_sock_udp: make 'remote match' condition more readable
gnrc_sock_udp: make 'remote match' condition more readable

RIOT-OS/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kaspar030/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,kaspar030/RIOT