gallium/st: fix shader_has_one_variant

I think we need to care about this here as well, otherwise the variant
logic might be short-circuited.

Fixes: 7eb5fd98fd ("mesa/st: handle running nir lower passes for ucp and psiz in tess stage")
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9631>

src/mesa/state_tracker/st_context.c

@@ -832,7 +832,8 @@ st_create_context_priv(struct gl_context *ctx, struct pipe_context *pipe,
          st->has_shareable_shaders &&
          !st->clamp_frag_depth_in_shader &&
          !st->clamp_vert_color_in_shader &&
-         !st->lower_point_size;
+         !st->lower_point_size &&
+         !st->lower_ucp;
 
    st->shader_has_one_variant[MESA_SHADER_GEOMETRY] =
          st->has_shareable_shaders &&