arm64: mm: Use corrent pte val in arch_vm_get_page_prot

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I96IZH



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During arch_vm_get_page_prot, vm_page_prot is init based on vma flags,
pte bit not vm_prot should be used here. Fix this problem by replacing
vm_prot with pte bit.

Fixes: 5c5063ac ("arm64: mm: Introduce VM_PBHA_BIT0 to enable pbha bit0 for single vma")
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>