audio_format: basic support for DSD-over-USB

src/decoder/flac_pcm.c

@@ -105,6 +105,7 @@ flac_convert(void *dest,
 	case SAMPLE_FORMAT_FLOAT:
 	case SAMPLE_FORMAT_DSD:
 	case SAMPLE_FORMAT_DSD_LSBFIRST:
+	case SAMPLE_FORMAT_DSD_OVER_USB:
 	case SAMPLE_FORMAT_UNDEFINED:
 		/* unreachable */
 		assert(false);