dhugetlb: isolate dynamic hugetlb code

hulk inclusion
category: feature
bugzilla: 46904, https://gitee.com/openeuler/kernel/issues/I6BDME


CVE: NA

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Add CONFIG_DYNAMIC_HUGETLB in struct mem_cgroup_extension and struct
hugetlbfs_inode_info to isolate the member.

Add CONFIG_DYNAMIC_HUGETLB for pageflag PG_pool to isolate it.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>