mm: Add reliable memory use limit for user tasks

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


CVE: NA

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there is a upper limit for special user tasks's memory allocation.
special user task means user task with reliable flag.

Init tasks will alloc memory from non-mirrored region if their allocation
trigger limit.

The limit can be set or access via /proc/sys/vm/task_reliable_limit

This limit's default value is ULONG_MAX.

Signed-off-by: Peng Wu <wupeng58@huawei.com>
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>