gnrc_netif_lorawan: Validate DR
gnrc_netif_lorawan: Validate DR

Co-authored-by: José Alamos <d922f027204096abdeb9f8914e6f5749da71284c@uc.cl>

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