Docs/mm/damon/design: clarify handling layer based filters evaluation sequence

If an element of memory matches a DAMOS filter, filters that installed
after that get no chance to make any effect to the element.  Hence in what
order DAMOS filters are handled is important, if both allow filters and
reject filters are used together.

The ordering is affected by both the installation order and which layter
the filters are handled.  The design document is not clearly documenting
the latter part.  Clarify it on the design doc.

Link: https://lkml.kernel.org/r/20250218223708.53437-5-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>