arm64: mm: Use subsequent bits to improve future compatibility for pbha

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



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Use subsequent bits to improve future compatibility which avoid conflicts
during backport.

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