anv/image: Simplify assertions in anv_image_from_swapchain()

anv/image: Simplify assertions in anv_image_from_swapchain()

No intended change in behavior.

Conceptual diff:
  |- assert(swapchain_image->apples == (pCreateInfo->apples + MORE));
  |  local_create_info->apples = pCreateInfo->apples + MORE;
  |+ assert(swapchain_image->apples == local_create_info->apples);

And, where appropriate:
  |- local_create_info->orange = X;
  |+ /* See spec anchor #swapchain-wsi-image-create-info .  */
  |+ assert(local_create_info->orange == X);

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/1466>