lavf/nutdec: add logging context to log

Add logging context to log, it's will help debuging.
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

libavformat/nutdec.c

@@ -1275,13 +1275,13 @@ static int read_seek(AVFormatContext *s, int stream_index,
         av_assert0(sp);
         pos2 = sp->back_ptr - 15;
     }
-    av_log(NULL, AV_LOG_DEBUG, "SEEKTO: %"PRId64"\n", pos2);
+    av_log(s, AV_LOG_DEBUG, "SEEKTO: %"PRId64"\n", pos2);
     pos = find_startcode(s->pb, SYNCPOINT_STARTCODE, pos2);
     avio_seek(s->pb, pos, SEEK_SET);
     nut->last_syncpoint_pos = pos;
-    av_log(NULL, AV_LOG_DEBUG, "SP: %"PRId64"\n", pos);
+    av_log(s, AV_LOG_DEBUG, "SP: %"PRId64"\n", pos);
     if (pos2 > pos || pos2 + 15 < pos)
-        av_log(NULL, AV_LOG_ERROR, "no syncpoint at backptr pos\n");
+        av_log(s, AV_LOG_ERROR, "no syncpoint at backptr pos\n");
     for (i = 0; i < s->nb_streams; i++)
         nut->stream[i].skip_until_key_frame = 1;