mm/dynamic_hugetlb: set PagePool to bad page

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6XOIE


CVE: NA

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Before discard the bad page, set PagePool flag to distinguish from free
page. And increase used_pages to guarantee used + freed = total.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>