makefiles/serial: fix indent
makefiles/serial: fix indent

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