iris: set the binding table size

we weren't doing mark_surface_used on images (i965 does it while
uploading the unnecessary image uniforms), so our binding tables were
too small...

src/gallium/drivers/iris/iris_program.c

@@ -310,9 +310,9 @@ assign_common_binding_table_offsets(const struct gen_device_info *devinfo,
    prog_data->binding_table.plane_start[2] = next_binding_table_offset;
    next_binding_table_offset += info->num_textures;
 
-   /* prog_data->base.binding_table.size will be set by brw_mark_surface_used. */
+   /* Set the binding table size */
+   prog_data->binding_table.size_bytes = next_binding_table_offset * 4;
 
-   //assert(next_binding_table_offset <= BRW_MAX_SURFACES);
    return next_binding_table_offset;
 }