cuvid: Fix flushing with new API/deinterlacing

Extra fields to reset.

libavcodec/cuvid.c

@@ -886,6 +886,10 @@ static void cuvid_flush(AVCodecContext *avctx)
     if (ret < 0)
         goto error;
 
+    ctx->prev_pts = INT64_MIN;
+    ctx->decoder_flushing = 0;
+    ctx->waiting_frames = 0;
+
     return;
  error:
     av_log(avctx, AV_LOG_ERROR, "CUDA reinit on flush failed\n");