Hide mkfifo.iq error message

src/gui/rpidatvtouch.c

@@ -515,7 +515,7 @@ void *DisplayFFT(void * arg)
 	fftwf_plan plan ;
 	plan = fftwf_plan_dft_1d(fft_size, fftin, fftout, FFTW_FORWARD, FFTW_ESTIMATE );
 
-	system("mkfifo fifo.iq");
+	system("mkfifo fifo.iq >/dev/null 2>/dev/null");
 	printf("Entering FFT thread\n");
 	pFileIQ = fopen("fifo.iq", "r");