net/skald : Enable configuration of 'SKALD_ADV_CHAN'
net/skald : Enable configuration of 'SKALD_ADV_CHAN'

Add macros to disable specific channels and move macros to
'CONFIG_' namespace

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