HACK Revert "h264: free the tables and uninitialize the context on flush"

This reverts commit 9eda9d3322.
This commit causes the flush inside the DXVA2 init to crash, so we cannot do this here.

The fix isn't required for our use-case anyway, since LAV always does a hard-flush when seeking H.264.

libavcodec/h264dec.c

@@ -519,9 +519,6 @@ static void h264_decode_flush(AVCodecContext *avctx)
     h->mb_y = 0;
     h->non_gray = 0;
 
-    ff_h264_free_tables(h);
-    h->context_initialized = 0;
-
     if (FF_HW_HAS_CB(avctx, flush))
         FF_HW_SIMPLE_CALL(avctx, flush);
 }