virgl: fix virgl_buffer_transfer_extend

Without setting hw_res, virgl_transfer_queue_extend never finds a
match and always returns NULL.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>

src/gallium/drivers/virgl/virgl_resource.c

@@ -554,6 +554,7 @@ static bool virgl_buffer_transfer_extend(struct pipe_context *ctx,
     * Pessimestically falls back if a flush is required.
     */
    dummy_trans.base.resource = resource;
+   dummy_trans.hw_res = vbuf->hw_res;
    dummy_trans.base.usage = usage;
    dummy_trans.base.box = *box;
    dummy_trans.base.stride = vbuf->metadata.stride[0];