tests/gnrc_sixlowpan: provide EUI-64 for dummy netdev
tests/gnrc_sixlowpan: provide EUI-64 for dummy netdev

The dummy netdev of this test doesn't provide any address. This adds at
least the IEEE 802.15.4 EUI-64 and makes the NETOPT_SRC_LEN option
dependent on it.

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