avcodec/dca: don't set initial sample_fmt

Valid sample_fmt will be set by dcadec_decode_frame() based on stream type.
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/dcadec.c

@@ -378,9 +378,6 @@ static av_cold int dcadec_init(AVCodecContext *avctx)
         break;
     }
 
-    avctx->sample_fmt = AV_SAMPLE_FMT_S32P;
-    avctx->bits_per_raw_sample = 24;
-
     return 0;
 }