at86rf2xx/at86rf2xx_netdev: improve documentation.
at86rf2xx/at86rf2xx_netdev: improve documentation.

It was not obvious where `dev->idle_state` was saved.

cladmi/RIOT,OTAkeys/RIOT,BytesGalore/RIOT,miri64/RIOT,toonst/RIOT,smlng/RIOT,basilfx/RIOT,biboc/RIOT,mfrey/RIOT,yogo1212/RIOT,mtausig/RIOT,biboc/RIOT,mtausig/RIOT,kaspar030/RIOT,lazytech-org/RIOT,jasonatran/RIOT,A-Paul/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,x3ro/RIOT,rfuentess/RIOT,miri64/RIOT,toonst/RIOT,ant9000/RIOT,basilfx/RIOT,OTAkeys/RIOT,biboc/RIOT,smlng/RIOT,rfuentess/RIOT,yogo1212/RIOT,OlegHahm/RIOT,rfuentess/RIOT,A-Paul/RIOT,A-Paul/RIOT,x3ro/RIOT,mfrey/RIOT,aeneby/RIOT,gebart/RIOT,miri64/RIOT,aeneby/RIOT,OlegHahm/RIOT,josephnoir/RIOT,authmillenon/RIOT,kYc0o/RIOT,A-Paul/RIOT,BytesGalore/RIOT,cladmi/RIOT,toonst/RIOT,lazytech-org/RIOT,x3ro/RIOT,lazytech-org/RIOT,cladmi/RIOT,authmillenon/RIOT,smlng/RIOT,kaspar030/RIOT,miri64/RIOT,aeneby/RIOT,ant9000/RIOT,BytesGalore/RIOT,BytesGalore/RIOT,biboc/RIOT,yogo1212/RIOT,toonst/RIOT,OlegHahm/RIOT,authmillenon/RIOT,OlegHahm/RIOT,ant9000/RIOT,josephnoir/RIOT,lazytech-org/RIOT,kYc0o/RIOT,A-Paul/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,basilfx/RIOT,jasonatran/RIOT,basilfx/RIOT,gebart/RIOT,kYc0o/RIOT,x3ro/RIOT,aeneby/RIOT,kaspar030/RIOT,yogo1212/RIOT,x3ro/RIOT,josephnoir/RIOT,gebart/RIOT,mfrey/RIOT,kaspar030/RIOT,miri64/RIOT,jasonatran/RIOT,rfuentess/RIOT,OlegHahm/RIOT,smlng/RIOT,jasonatran/RIOT,cladmi/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,mtausig/RIOT,mtausig/RIOT,mtausig/RIOT,cladmi/RIOT,kaspar030/RIOT,jasonatran/RIOT,biboc/RIOT,ant9000/RIOT,josephnoir/RIOT,yogo1212/RIOT,lazytech-org/RIOT,mfrey/RIOT,kYc0o/RIOT,toonst/RIOT,OTAkeys/RIOT,authmillenon/RIOT,basilfx/RIOT,josephnoir/RIOT,RIOT-OS/RIOT,rfuentess/RIOT,ant9000/RIOT,authmillenon/RIOT,gebart/RIOT,aeneby/RIOT,smlng/RIOT,gebart/RIOT,OTAkeys/RIOT,kYc0o/RIOT,BytesGalore/RIOT,RIOT-OS/RIOT,mfrey/RIOT