spektrum-scanner: adapt to new gnrc_netif calls
spektrum-scanner: adapt to new gnrc_netif calls

Accessing and handling of network interfaces with gnrc_netif has changed
and needs adaption to compile and work again.

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