Docs/admin-guide/mm/damon/usage: update for {core,ops}_filters directories

Document {core,ops}_filters directories on usage document.

Link: https://lkml.kernel.org/r/20250305222733.59089-9-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>