mm: add cmdline for the reliable memory usage of page cache

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


CVE: NA

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Add cmdline for the reliable memory usage of page cache.
Page cache will not use reliable memory when passing option
"P" to reliable_debug in cmdline.

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