Revert "avformat/demux: Count EAGAIN as 100 bytes in relation to read limit in avformat_find_stream_info()"

Modifying avformat_find_stream_info() behaviour based on the number of EAGAINs
it encounters is a hack which usually only hides the real issue if such thing
happen.

This reverts commit b0cac7082d.

libavformat/demux.c

@@ -2615,10 +2615,8 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
         /* NOTE: A new stream can be added there if no header in file
          * (AVFMTCTX_NOHEADER). */
         ret = read_frame_internal(ic, pkt1);
-        if (ret == AVERROR(EAGAIN)) {
-            read_size += 100;
+        if (ret == AVERROR(EAGAIN))
             continue;
-        }
 
         if (ret < 0) {
             /* EOF or error*/