mm: memcontrol: privatize memcg_page_state query functions

mainline inclusion
from mainline-v5.13-rc1
commit a18e6e6e
category: feature
bugzilla: 185803 https://gitee.com/openeuler/kernel/issues/I4JOG9?from=project-issue
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a18e6e6e150a

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There are no users outside of the memory controller itself. The rest
of the kernel cares either about node or lruvec stats.

Link: https://lkml.kernel.org/r/20210209163304.77088-4-hannes@cmpxchg.org


Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Conflict:
	include/linux/memcontrol.h
Signed-off-by: Lu Jialin <lujialin4@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>