libavutil/hwcontext_qsv: fix a bug for mapping vaapi frame to qsv

The data stored in data[3] in VAAPI AVFrame is VASurfaceID while
the data stored in pair->first is the pointer of VASurfaceID, so
we need to do cast to make following commandline works:

ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 \
-hwaccel_output_format vaapi -i input.264 \
-vf "hwmap=derive_device=qsv,format=qsv" -c:v h264_qsv output.264

Signed-off-by: nyanmisaka <nst799610810@gmail.com>
Signed-off-by: Wenbin Chen <wenbin.chen@intel.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavutil/hwcontext_qsv.c

@@ -1218,7 +1218,7 @@ static int qsv_map_to(AVHWFramesContext *dst_ctx,
         case AV_PIX_FMT_VAAPI:
         {
             mfxHDLPair *pair = (mfxHDLPair*)hwctx->surfaces[i].Data.MemId;
-            if (pair->first == src->data[3]) {
+            if (*(VASurfaceID*)pair->first == (VASurfaceID)src->data[3]) {
                 index = i;
                 break;
             }