avformat/matroskadec: Fix seeking

matroska_reset_status (a function that is used during seeking (among
other things)) used an int for the return value of avio_seek which
returns an int64_t. Checking the return value then indicated an error
even though the seek was successfull for targets in the range of
2GB-4GB, 6GB-8GB, ... This error implied that the status hasn't been
reset and in particular, the old level was still considered to be in
force, so that ebml_parse returned errors because the newly parsed
elements were of course not contained in the previously active and still
wrongly considered active master element any more.

Addresses ticket #8084.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/matroskadec.c

@@ -757,7 +757,7 @@ static int matroska_reset_status(MatroskaDemuxContext *matroska,
                                  uint32_t id, int64_t position)
 {
     if (position >= 0) {
-        int err = avio_seek(matroska->ctx->pb, position, SEEK_SET);
+        int64_t err = avio_seek(matroska->ctx->pb, position, SEEK_SET);
         if (err < 0)
             return err;
     }