mm/damon: use 'struct damon_target *' instead of 'void *' in target_valid()

mainline inclusion
from mainline-v6.2-rc6
commit 16bc1b0f
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=16bc1b0f0269b6110f6d25880b52947d354e2980

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We could use 'struct damon_target *' directly instead of 'void *' in
target_valid() operation to make code simple.

Link: https://lkml.kernel.org/r/1663241621-13293-1-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>
Signed-off-by: Ze Zuo <zuoze1@huawei.com>