matroskadec: return AVERROR_EOF upon detection of end of file

Originally committed as revision 17460 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/matroskadec.c

@@ -1761,7 +1761,7 @@ static int matroska_read_packet(AVFormatContext *s, AVPacket *pkt)
 
     while (matroska_deliver_packet(matroska, pkt)) {
         if (matroska->done)
-            return AVERROR(EIO);
+            return AVERROR_EOF;
         matroska_parse_cluster(matroska);
     }