mm/damon/sysfs: remove damon_sysfs_destroy_targets()

mm/damon/sysfs: remove damon_sysfs_destroy_targets()

The function was introduced for putting pids and deallocating unnecessary
targets.  Hence it is called before damon_destroy_ctx().  Now vaddr puts
pid for each target destruction (cleanup_target()).  damon_destroy_ctx()
deallocates the targets anyway.  So damon_sysfs_destroy_targets() has no
reason to exist.  Remove it.

Link: https://lkml.kernel.org/r/20250712195016.151108-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>