frontends/va/enc: hardcode h265 encoder ref pic list size

Set the size of the ref pic list0 for the h265 encoder to 1.

Signed-off-by: Thong Thai <thong.thai@amd.com>
Reviewed-by: Boyuan Zhang <boyuan.zhang@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13915>

src/gallium/frontends/va/picture_hevc_enc.c

@@ -128,6 +128,7 @@ vlVaHandleVAEncSequenceParameterBufferTypeHEVC(vlVaDriver *drv, vlVaContext *con
    VAEncSequenceParameterBufferHEVC *h265 = (VAEncSequenceParameterBufferHEVC *)buf->data;
 
    if (!context->decoder) {
+      context->templat.max_references = 1;
       context->templat.level = h265->general_level_idc;
       context->decoder = drv->pipe->create_video_codec(drv->pipe, &context->templat);