mm/vmalloc: Extend vmalloc usage about hugepage

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



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This allow the user to do huge vmalloc and remap those hugepage range
into userspace.

Some devices could not handle mixed levels of page table. They want to
know exactly if the memory thay alloced is hugepages or not. Introduce
vmalloc/vmap/remap interfaces that handle only hugepages.

Introduce VM_HUGE_PAGES flag. __vmalloc_node_range() would alloc
PMD_SIZE hugepages if specifying VM_HUGE_PAGES.

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