mm: fix statistic of ReliableTaskUsed

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SK3S


CVE: NA

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Previous method of accounting ReliableTaskUsed is inaccurate,
such as in cow, migration, shareable memory, which will lead
to overflow.

Fix statistic of ReliableTaskUsed by accounting reliable
anon page and reliable page cache.

Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>