mm: Introduce proc interface to control memory reliable features

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


CVE: NA

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Introduce proc interface to control memory reliable features.
These functions can be controlled via access /proc/sys/vm/reliable_debug.

Four bits are used to represent the following features
- bit 0: memory reliable feature
- bit 1: reliable fallback feature
- bit 2: tmpfs use reliable memory feature
- bit 3: pagecache use reliable memory feature

Bit 1~3 are valid if and only if the bit 0 is 1. If the first bit is 0, all
other features will be closed no matter other bits's status.

For example, you can enable reliable fallback feature by

	$ echo 3 > /proc/sys/vm/reliable_debug

Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Kefeng <Wang&lt;wangkefeng.wang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>