mm: Add support for limiting the usage of reliable memory in pagecache

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


CVE: NA

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Add interface /proc/sys/vm/reliable_pagecache_max_bytes to set the
max size for reliable page cache, the max size cant beyond total
reliable ram.

the whole reliable memory feature depend on kernelcore=mirror,
and which depend on NUMA, so remove redundant code in UMA.

Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>