memcg: cleanup with !CONFIG_MEMCG_V1

Extern declarations have no definitions with !CONFIG_MEMCG_V1 and no
users, drop them altogether.

Link: https://lkml.kernel.org/r/20240909163223.3693529-1-mkoutny@suse.com
Link: https://lkml.kernel.org/r/20240909163223.3693529-2-mkoutny@suse.comSigned-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Chen Ridong <chenridong@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcontrol-v1.h

@@ -154,8 +154,6 @@ static inline bool memcg1_charge_skmem(struct mem_cgroup *memcg, unsigned int nr
 				       gfp_t gfp_mask) { return true; }
 static inline void memcg1_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages) {}
 
-extern struct cftype memsw_files[];
-extern struct cftype mem_cgroup_legacy_files[];
 #endif	/* CONFIG_MEMCG_V1 */
 
 #endif	/* __MM_MEMCONTROL_V1_H */