qsvdec: Fix running with assert_level > 0

Assertion avctx->codec_id != AV_CODEC_ID_NONE failed at src/libavcodec/parser.c:128

The setting on the internal AVCodecContext used for parsing only is
otherwise irrelevant, so just set it to avoid the assert.

libavcodec/qsvdec.c

@@ -501,6 +501,8 @@ int ff_qsv_process_data(AVCodecContext *avctx, QSVContext *q,
         if (!q->avctx_internal)
             return AVERROR(ENOMEM);
 
+        q->avctx_internal->codec_id = avctx->codec_id;
+
         q->parser = av_parser_init(avctx->codec_id);
         if (!q->parser)
             return AVERROR(ENOMEM);