mm: add free_hot_cold_page_list() helper from https://github.com/faux123/tuna/commit/30421791a40d9bd87a3780e48d3ef63cb82d8642
mm: collect LRU list heads into struct lruvec from https://github.com/faux123/tuna/commit/80193636cf1f02380b5306c8b74de7b113c405d8