avformat: move AVStream.{parser,need_parsing} to AVStreamInternal

Those are private fields, no reason to have them exposed in a public
header.

Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/mpeg.c

@@ -623,7 +623,7 @@ skip:
         st->codecpar->sample_rate = 8000;
     }
     st->internal->request_probe     = request_probe;
-    st->need_parsing      = AVSTREAM_PARSE_FULL;
+    st->internal->need_parsing      = AVSTREAM_PARSE_FULL;
 
 found:
     if (st->discard >= AVDISCARD_ALL)