mm: mem_reliable: Add cmdline reliable_debug to enable separate feature

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8USBA


CVE: NA

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Add kernel param reliable_debug to enable separate memory reliable
features on demand:
- Page cache will not use reliable memory when passing option "P" to
  reliable_debug in cmdline.
- Shmem will not use reliable memory when passing opiton "S" to
  reliable_debug in cmdline.

Signed-off-by: Peng Wu <wupeng58@huawei.com>
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>