mm, memcg: remove unused functions

Since commit 2d146aa3 ("mm: memcontrol: switch to rstat"), last user
of memcg_stat_item_in_bytes() is gone.  And since commit fa40d1ee
("mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node()"), only
the declaration of mem_cgroup_select_victim_node() is remained here.
Remove them.

Link: https://lkml.kernel.org/r/20210807082835.61281-2-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NShakeel Butt <shakeelb@google.com>
Reviewed-by: NMuchun Song <songmuchun@bytedance.com>
Acked-by: NRoman Gushchin <guro@fb.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -593,13 +593,6 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page)
 }
 #endif
 
-static __always_inline bool memcg_stat_item_in_bytes(int idx)
-{
-	if (idx == MEMCG_PERCPU_B)
-		return true;
-	return vmstat_item_in_bytes(idx);
-}
-
 static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
 {
 	return (memcg == root_mem_cgroup);
@@ -904,11 +897,6 @@ static inline bool mem_cgroup_online(struct mem_cgroup *memcg)
 	return !!(memcg->css.flags & CSS_ONLINE);
 }
 
-/*
- * For memory reclaim.
- */
-int mem_cgroup_select_victim_node(struct mem_cgroup *memcg);
-
 void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
 		int zid, int nr_pages);