sx127x: fix for sending in implicit headers mode
sx127x: fix for sending in implicit headers mode

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