mm: make page cache use reliable memory by default

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


CVE: NA

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__page_cache_alloc is used to alloc page cache in most file system,
such as ext4, f2fs, so add ___GFP_RELIABILITY flag to support feature
CONFIG_MEMORY_RELIABLE when alloc page.

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