pan/midgard: Set .shadow for shadow samplers

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3125>

src/panfrost/midgard/midgard_compile.c

@@ -1725,6 +1725,7 @@ emit_texop_native(compiler_context *ctx, nir_tex_instr *instr,
                         .out_full = 1,
 
                         .sampler_type = midgard_sampler_type(instr->dest_type),
+                        .shadow = instr->is_shadow,
                 }
         };