Only skip MLP header in mpeg files if the codec actually is MLP.

Fixes PCM audio in Kansas Pheasant Hunt 2000 mpg file.
Reported-by: Mashiat Sarker Shakkhar

libavformat/mpeg.c

@@ -504,7 +504,7 @@ static int mpegps_read_packet(AVFormatContext *s,
     if(st->discard >= AVDISCARD_ALL)
         goto skip;
     if (startcode >= 0xa0 && startcode <= 0xaf) {
-      if (lpcm_header_len == 6) {
+      if (lpcm_header_len == 6 && st->codec->codec_id == AV_CODEC_ID_MLP) {
             if (len < 6)
                 goto skip;
             avio_skip(s->pb, 6);