mm: mem_reliable: Alloc pagecache from reliable region

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


CVE: NA

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filemap_alloc_folio is used to alloc page cache in most file system,
such as ext4, f2fs, so add GFP_RELIABLE flag to use reliable
memory when alloc page cache.

Signed-off-by: Chen Wandun <chenwandun@huawei.com>