usrp/fft.c (do_fft): don't output the sample number when dumping
usrp/fft.c (do_fft): don't output the sample number when dumping

gnuplot already maintains the sample count in $0

cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan