mm/hugetlb: Introduce alloc_hugetlb_folio_size()

ascend inclusion
category: Feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8SC4J



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This could allocate hugepage from hpool of specific size.
The driver would map those hugepage for some special processes via
hugetlb_insert_hugepage_pte().

Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>