arm64: support huge vmalloc mappings

As commit 559089e0

 ("vmalloc: replace VM_NO_HUGE_VMAP with
VM_ALLOW_HUGE_VMAP"), the use of hugepage mappings for vmalloc
is an opt-in strategy, so it is saftly to support huge vmalloc
mappings on arm64, for now, it is used in kvmalloc() and
alloc_large_system_hash().

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Link: https://lore.kernel.org/r/20220911044423.139229-1-wangkefeng.wang@huawei.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>