Fix VA-API decoding artefacts.

Fixes ticket #457.

libavcodec/vaapi_h264.c

@@ -282,7 +282,8 @@ static int start_frame(AVCodecContext          *avctx,
     if (!iq_matrix)
         return -1;
     memcpy(iq_matrix->ScalingList4x4, h->pps.scaling_matrix4, sizeof(iq_matrix->ScalingList4x4));
-    memcpy(iq_matrix->ScalingList8x8, h->pps.scaling_matrix8, sizeof(iq_matrix->ScalingList8x8));
+    memcpy(iq_matrix->ScalingList8x8[0], h->pps.scaling_matrix8[0], sizeof(iq_matrix->ScalingList8x8[0]));
+    memcpy(iq_matrix->ScalingList8x8[1], h->pps.scaling_matrix8[3], sizeof(iq_matrix->ScalingList8x8[0]));
     return 0;
 }