Docs/admin-guide/damon: add a document for DAMON_LRU_SORT

This commit documents the usage of DAMON_LRU_SORT for admins.

Link: https://lkml.kernel.org/r/20220613192301.8817-10-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/admin-guide/mm/damon/index.rst

@@ -14,3 +14,4 @@ optimize those.
    start
    usage
    reclaim
+   lru_sort