semtech-loramac: avoid explicit cast to netdev
semtech-loramac: avoid explicit cast to netdev

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