Docs/admin-guide/mm/damon/usage: update the ways for getting monitoring results

The recommended ways for getting DAMON monitoring results are using
tried_regions sysfs directory for partial snapshot of the results, and
DAMON tracepoint for full record of the results.  However, the
tried_regions sysfs directory usage has not sufficiently updated on some
sections of the DAMON usage document.  Update those.

Link: https://lkml.kernel.org/r/20230616191742.87531-8-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>