mm/damon: get the hotness from damon_hot_score() in damon_pageout_score()

We can get the hotness value from damon_hot_score() directly in
damon_pageout_score() function and improve the code readability.

Link: https://lkml.kernel.org/r/1661766366-20998-1-git-send-email-kaixuxia@tencent.com


Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>