iris: Actually pin the scratch BO.

We were pinning it for compute shaders, and pinning it when restoring
saved buffers, but we never actually pinned it in the original batch
for VS/TCS/TES/GS/FS.

Fixes rendering in GFXBench5's Tessellation demo and a bunch of Piglit
geometry shader tests.

src/gallium/drivers/iris/iris_state.c

@@ -4593,8 +4593,16 @@ iris_upload_dirty_render_state(struct iris_context *ice,
       struct iris_compiled_shader *shader = ice->shaders.prog[stage];
 
       if (shader) {
+         struct brw_stage_prog_data *prog_data = shader->prog_data;
          struct iris_resource *cache = (void *) shader->assembly.res;
          iris_use_pinned_bo(batch, cache->bo, false);
+
+         if (prog_data->total_scratch > 0) {
+            struct iris_bo *bo =
+               iris_get_scratch_space(ice, prog_data->total_scratch, stage);
+            iris_use_pinned_bo(batch, bo, true);
+         }
+
          iris_batch_emit(batch, shader->derived_data,
                          iris_derived_program_state_size(stage));
       } else {