compositor: fix surface pointer cast

In weston, the wl_resource:data field for a wl_surface object always
contains struct weston_surface *, never struct wl_surface *.

Even though this is just a cosmetic fix, it should reduce confusion.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

src/compositor.c

@@ -1985,8 +1985,7 @@ pointer_set_cursor(struct wl_client *client, struct wl_resource *resource,
 	struct weston_surface *surface = NULL;
 
 	if (surface_resource)
-		surface = container_of(surface_resource->data,
-				       struct weston_surface, surface);
+		surface = surface_resource->data;
 
 	if (seat->seat.pointer->focus == NULL)
 		return;