mm/damon/sysfs: update schemes stat in the kdamond context

mm/damon/sysfs: update schemes stat in the kdamond context

Only '->kdamond' and '->kdamond_stop' are protected by 'kdamond_lock' of
'struct damon_ctx'.  All other DAMON context internal data items are
recommended to be accessed in DAMON callbacks, or under some additional
synchronizations.  But, DAMON sysfs is accessing the schemes stat under
'kdamond_lock'.

It makes no big issue as the read values are not used anywhere inside
kernel, but would better to be fixed.  This commit moves the reads to
DAMON callback context, as supposed to be used for the purpose.

Link: https://lkml.kernel.org/r/20220429160606.127307-11-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>