iris: Fix SLM

Now that Jason has set up the L3 we can do this.  Also, my assert was
useless because we hadn't set up the field in the first place.  Oops.

src/gallium/drivers/iris/iris_program.c

@@ -1138,6 +1138,8 @@ iris_compile_cs(struct iris_context *ice,
 
    cs_prog_data->binding_table.work_groups_start = 0;
 
+   prog_data->total_shared = nir->info.cs.shared_size;
+
    iris_setup_uniforms(compiler, mem_ctx, nir, prog_data, &system_values,
                        &num_system_values);