Docs/mm/damon/design: document allow/reject DAMOS filter behaviors

Update DAMOS filters design document to describe the allow/reject behavior
of filters.

Link: https://lkml.kernel.org/r/20250109175126.57878-8-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>