mm/damon: remove return value from before_terminate callback

mainline inclusion
from mainline-5.16
commit 658f9ae7
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4GVMK
CVE: NA

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Since the return value of 'before_terminate' callback is never used, we
make it have no return value.

Link: https://lkml.kernel.org/r/20211029005023.8895-1-changbin.du@gmail.com


Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 658f9ae7)
Signed-off-by: Yue Zou <zouyue3@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>