lavf/matroskadec: correct codec_tag for "SMI" SVQ3 files

This corrects the codec_tag for some SVQ3 files
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/matroskadec.c

@@ -1878,8 +1878,10 @@ static int matroska_parse_tracks(AVFormatContext *s)
                 fourcc   = AV_RL32(track->codec_priv.data);
                 codec_id = ff_codec_get_id(ff_codec_movvideo_tags, fourcc);
             }
-            if (codec_id == AV_CODEC_ID_NONE && AV_RL32(track->codec_priv.data+4) == AV_RL32("SMI "))
-                codec_id = AV_CODEC_ID_SVQ3;
+            if (codec_id == AV_CODEC_ID_NONE && AV_RL32(track->codec_priv.data+4) == AV_RL32("SMI ")) {
+                fourcc = MKTAG('S','V','Q','3');
+                codec_id = ff_codec_get_id(ff_codec_movvideo_tags, fourcc);
+            }
             if (codec_id == AV_CODEC_ID_NONE) {
                 char buf[32];
                 av_get_codec_tag_string(buf, sizeof(buf), fourcc);