mm/damon/sysfs: remove unused code for schemes tried regions update

DAMON sysfs interface was using damon_callback with its own complicated
synchronization logics to update DAMOS scheme applied regions directories
and files.  But it is replaced to use damos_walk(), and the additional
synchronization logics are no more being used.  Remove those.

Link: https://lkml.kernel.org/r/20250103174400.54890-11-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>