mm: memcontrol: fix swap counter leak from offline cgroup

mm: memcontrol: fix swap counter leak from offline cgroup

commit 73f839b6d2ed addressed an issue regarding the swap counter leak
that occurred from an offline cgroup.  However, commit 89ce924f0bd4
modified the parameter from @swap_memcg to @memcg (presumably this
alteration was introduced while resolving conflicts).  Fix this problem by
reverting this minor change.

Link: https://lkml.kernel.org/r/20250410081812.10073-1-songmuchun@bytedance.com
Fixes: 89ce924f0bd4 ("mm: memcontrol: move memsw charge callbacks to v1")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>