mm/damon/sysfs: use damon_call() for update_schemes_stats

DAMON sysfs interface uses damon_callback with its own synchronization
facility to handle update_schemes_stats kdamond command.  But damon_call()
can support the use case without the additional synchronizations.  Convert
the code to use damon_call() instead.

Link: https://lkml.kernel.org/r/20250103174400.54890-5-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>