boards/iotlab: fix saul gpio configuration
boards/iotlab: fix saul gpio configuration

take into account inversion of LEDs and initialize them cleared

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