mm/list_lru.c: remove unused list_lru_from_kmem()

mm/list_lru.c: remove unused list_lru_from_kmem()

Fixes: 0a97c01cd20bb ("list_lru: allow explicit memcg and NUMA node selection)
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312141318.q8b5yrAq-lkp@intel.com/
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>