Docs/admin-guide/mm/damon/lru_sort: document addr_unit parameter

Docs/admin-guide/mm/damon/lru_sort: document addr_unit parameter

Commit 2e0fe9245d6b ("mm/damon/lru_sort: support addr_unit for
DAMON_LRU_SORT") introduced the 'addr_unit' parameter for DAMON_LRU_SORT.
But the usage document is not updated for that.  Update the document.

Link: https://lkml.kernel.org/r/20251026182216.118200-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>