anv/image: Add an aux_usage field for "default" aux

Initially, the field is set to ISL_AUX_USAGE_NONE so this commit shouldn't
bring any functional changes.  Setting this field to something else will
cause all sampled and storage image views to be created with AUX and blorp
will start trying to respect it so set with care.

src/intel/vulkan/anv_private.h

@@ -1555,6 +1555,9 @@ struct anv_image {
       };
    };
 
+   /** The aux usage for this surface when outside a render pass */
+   enum isl_aux_usage aux_usage;
+
    struct anv_surface aux_surface;
 };