mm/damon/Kconfig: notify debugfs deprecation plan

mm/damon/Kconfig: notify debugfs deprecation plan

Commit b18402726bd1 ("Docs/admin-guide/mm/damon/usage: document DAMON
sysfs interface") announced the DAMON debugfs interface deprecation plan,
but it is not so aggressively announced.  As the deprecation time is
coming, this commit makes the announce more easy to be found by adding the
note to the config menu of DAMON debugfs interface.

Link: https://lkml.kernel.org/r/20220909202901.57977-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Yun Levi <ppbuk5246@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>