xbee: provide NETOPT_PROTO
xbee: provide NETOPT_PROTO

Fixes #6973.

The current 6Lo-ND implementation relies on `NETOPT_PROTO` being
returned for an IEEE 802.15.4 device. This isn't ideal, since it mixes
GNRC into device code (and the next iteration of NDP will do it
better), but for now this is the only way to fix #6973.

plushvoxel/RIOT,Josar/RIOT,mfrey/RIOT,thomaseichinger/RIOT,hamilton-mote/RIOT-OS,OlegHahm/RIOT,Josar/RIOT,kerneltask/RIOT,Josar/RIOT,adjih/RIOT,adrianghc/RIOT,beurdouche/RIOT,LudwigOrtmann/RIOT,kerneltask/RIOT,kerneltask/RIOT,BytesGalore/RIOT,rfuentess/RIOT,adrianghc/RIOT,kaleb-himes/RIOT,kaspar030/RIOT,A-Paul/RIOT,avmelnikoff/RIOT,LudwigOrtmann/RIOT,neiljay/RIOT,kerneltask/RIOT,gebart/RIOT,cladmi/RIOT,adrianghc/RIOT,thomaseichinger/RIOT,BytesGalore/RIOT,kbumsik/RIOT,kbumsik/RIOT,lazytech-org/RIOT,cladmi/RIOT,kaleb-himes/RIOT,miri64/RIOT,miri64/RIOT,ant9000/RIOT,kaspar030/RIOT,LudwigKnuepfer/RIOT,OTAkeys/RIOT,ks156/RIOT,plushvoxel/RIOT,mtausig/RIOT,adjih/RIOT,miri64/RIOT,jfischer-phytec-iot/RIOT,rfuentess/RIOT,lazytech-org/RIOT,cladmi/RIOT,neumodisch/RIOT,jasonatran/RIOT,hamilton-mote/RIOT-OS,biboc/RIOT,immesys/RiSyn,OlegHahm/RIOT,LudwigOrtmann/RIOT,RIOT-OS/RIOT,mtausig/RIOT,beurdouche/RIOT,neiljay/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,jfischer-phytec-iot/RIOT,neumodisch/RIOT,neumodisch/RIOT,OTAkeys/RIOT,mfrey/RIOT,josephnoir/RIOT,hamilton-mote/RIOT-OS,lazytech-org/RIOT,yogo1212/RIOT,kYc0o/RIOT,jfischer-phytec-iot/RIOT,basilfx/RIOT,authmillenon/RIOT,cladmi/RIOT,immesys/RiSyn,ant9000/RIOT,josephnoir/RIOT,kbumsik/RIOT,x3ro/RIOT,kbumsik/RIOT,x3ro/RIOT,LudwigKnuepfer/RIOT,hamilton-mote/RIOT-OS,roberthartung/RIOT,biboc/RIOT,ks156/RIOT,beurdouche/RIOT,gebart/RIOT,smlng/RIOT,gebart/RIOT,mfrey/RIOT,smlng/RIOT,LudwigOrtmann/RIOT,plushvoxel/RIOT,josephnoir/RIOT,basilfx/RIOT,jasonatran/RIOT,OTAkeys/RIOT,josephnoir/RIOT,neiljay/RIOT,adrianghc/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,aeneby/RIOT,smlng/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,biboc/RIOT,BytesGalore/RIOT,kYc0o/RIOT,immesys/RiSyn,ks156/RIOT,basilfx/RIOT,roberthartung/RIOT,neumodisch/RIOT,toonst/RIOT,mtausig/RIOT,yogo1212/RIOT,avmelnikoff/RIOT,josephnoir/RIOT,LudwigKnuepfer/RIOT,rfuentess/RIOT,beurdouche/RIOT,x3ro/RIOT,ant9000/RIOT,toonst/RIOT,smlng/RIOT,LudwigKnuepfer/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,yogo1212/RIOT,kerneltask/RIOT,gebart/RIOT,kaleb-himes/RIOT,mtausig/RIOT,roberthartung/RIOT,avmelnikoff/RIOT,neumodisch/RIOT,adjih/RIOT,roberthartung/RIOT,miri64/RIOT,kaleb-himes/RIOT,Josar/RIOT,thomaseichinger/RIOT,LudwigOrtmann/RIOT,authmillenon/RIOT,adjih/RIOT,OlegHahm/RIOT,rfuentess/RIOT,immesys/RiSyn,basilfx/RIOT,thomaseichinger/RIOT,plushvoxel/RIOT,aeneby/RIOT,kaleb-himes/RIOT,kYc0o/RIOT,LudwigKnuepfer/RIOT,ant9000/RIOT,yogo1212/RIOT,jasonatran/RIOT,neumodisch/RIOT,kaspar030/RIOT,A-Paul/RIOT,toonst/RIOT,jasonatran/RIOT,beurdouche/RIOT,cladmi/RIOT,ks156/RIOT,x3ro/RIOT,roberthartung/RIOT,smlng/RIOT,ant9000/RIOT,mtausig/RIOT,LudwigOrtmann/RIOT,A-Paul/RIOT,mfrey/RIOT,basilfx/RIOT,jasonatran/RIOT,aeneby/RIOT,BytesGalore/RIOT,x3ro/RIOT,authmillenon/RIOT,toonst/RIOT,immesys/RiSyn,RIOT-OS/RIOT,hamilton-mote/RIOT-OS,adrianghc/RIOT,toonst/RIOT,OlegHahm/RIOT,ks156/RIOT,biboc/RIOT,biboc/RIOT,immesys/RiSyn,plushvoxel/RIOT,A-Paul/RIOT,jfischer-phytec-iot/RIOT,lazytech-org/RIOT,authmillenon/RIOT,thomaseichinger/RIOT,gebart/RIOT,BytesGalore/RIOT,OlegHahm/RIOT,authmillenon/RIOT,OTAkeys/RIOT,kbumsik/RIOT,aeneby/RIOT,kaspar030/RIOT,mfrey/RIOT,adjih/RIOT,Josar/RIOT,neiljay/RIOT,miri64/RIOT,neiljay/RIOT,A-Paul/RIOT,jfischer-phytec-iot/RIOT,kaspar030/RIOT,rfuentess/RIOT,RIOT-OS/RIOT,lazytech-org/RIOT,aeneby/RIOT,OTAkeys/RIOT