mm/damon/sysfs-schemes: call missing mem_cgroup_iter_break()

mm/damon/sysfs-schemes: call missing mem_cgroup_iter_break()

damon_sysfs_memcg_path_to_id() breaks mem_cgroup_iter() loop without
calling mem_cgroup_iter_break().  This leaks the cgroup reference.  Fix
the issue by calling mem_cgroup_iter_break() before the break.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260426173625.86521-1-sj@kernel.org
Link: https://lore.kernel.org/20260423004148.74722-1-sj@kernel.org
Fixes: 29cbb9a13f05 ("mm/damon/sysfs-schemes: implement scheme filters")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 6.3.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>