lavc/vaapi_encode_h264: correct VUI max_dec_frame_buffering setting

This should refer to the existing SPS structure, not the VAAPI sequence
parameter buffer (which is not yet initialised).
Signed-off-by: Jun Zhao <jun.zhao@intel.com>
Signed-off-by: Wang, Yi A <yi.a.wang@intel.com>
Signed-off-by: Mark Thompson <sw@jkqxz.net>

libavcodec/vaapi_encode_h264.c

@@ -441,7 +441,7 @@ static int vaapi_encode_h264_init_sequence_params(AVCodecContext *avctx)
     sps->vui.log2_max_mv_length_horizontal = 16;
     sps->vui.log2_max_mv_length_vertical   = 16;
     sps->vui.max_num_reorder_frames        = (ctx->b_per_p > 0);
-    sps->vui.max_dec_frame_buffering       = vseq->max_num_ref_frames;
+    sps->vui.max_dec_frame_buffering       = sps->max_num_ref_frames;
 
     pps->nal_unit_header.nal_ref_idc = 3;
     pps->nal_unit_header.nal_unit_type = H264_NAL_PPS;