mm/sharepool: Change data type of members in sp_spa_stat to atomic64.

hulk inclusion
category: other
bugzilla: https://gitee.com/openeuler/kernel/issues/I6GI0X



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Member of sp_spa_stat is changed to atomic64_t to
solve the concurrency problem.Spa_stat no longer
needs sp_area_lock protection.

Signed-off-by: Xu Qiang <xuqiang36@huawei.com>