mm: Use wrapper to fix KABI broken in struct mempolicy

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6I1Z2


CVE: NA

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Since struct mempolicy is commonly used by external users, use wrapper
to fix KABI broken in struct mempolicy.

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