lwip: activate TCP_LISTEN_BACKLOG per default with `sock_tcp`
lwip: activate TCP_LISTEN_BACKLOG per default with `sock_tcp`

Prevents unnecessary usage of resources, as the queue of `sock_tcp` is
restricted.

smlng/RIOT,kYc0o/RIOT,kaspar030/RIOT,ant9000/RIOT,kYc0o/RIOT,authmillenon/RIOT,authmillenon/RIOT,ant9000/RIOT,basilfx/RIOT,jasonatran/RIOT,smlng/RIOT,yogo1212/RIOT,OlegHahm/RIOT,basilfx/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,yogo1212/RIOT,kaspar030/RIOT,jasonatran/RIOT,smlng/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,miri64/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,ant9000/RIOT,OTAkeys/RIOT,basilfx/RIOT,authmillenon/RIOT,ant9000/RIOT,authmillenon/RIOT,yogo1212/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,smlng/RIOT,OlegHahm/RIOT,ant9000/RIOT,kYc0o/RIOT,kaspar030/RIOT,basilfx/RIOT,miri64/RIOT,jasonatran/RIOT,OlegHahm/RIOT,jasonatran/RIOT,miri64/RIOT,authmillenon/RIOT,OTAkeys/RIOT,authmillenon/RIOT,kaspar030/RIOT,kYc0o/RIOT,jasonatran/RIOT,miri64/RIOT,OTAkeys/RIOT,kYc0o/RIOT,basilfx/RIOT,smlng/RIOT,yogo1212/RIOT,miri64/RIOT,OlegHahm/RIOT