mm/damon/core: split out scheme stat update logic into a new function

mainline inclusion
from mainline-v6.2-rc6
commit d1cbbf62
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6MRUG

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d1cbbf621fc25950938be74a228ef518d05d93a1

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The function for applying a given DAMON scheme action to a given DAMON
region, 'damos_apply_scheme()' is not quite short.  Make it better to read
by splitting out the stat update logic into a new function.

Link: https://lkml.kernel.org/r/20221026225943.100429-4-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ze Zuo <zuoze1@huawei.com>