mm/sharepool: Implement mg_sp_make_share_k2u()

ascend inclusion
category: Feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8LNGH



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This share a kernel vmalloc memory range to userspace via
remap_pfn_range()/hugetlb_insert_hugepage_pte().

The hugepages remap to userspace is specail map and no need to clean
the rmap and manage the dirty bit in __unmap_hugepage_range.

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