arm64: mm: Restore mm_cpumask (revert commit 38d96287 ("arm64: mm: kill mm_cpumask usage"))

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4BLL0


CVE: NA

---------------------------

mm_cpumask was deleted by the commit 38d96287 ("arm64: mm: kill
mm_cpumask usage") because it was not used at that time. Now this is needed
to find appropriate CPUs for TLB flush, so this patch reverts this commit.

Signed-off-by: QI Fuli <qi.fuli@fujitsu.com>
Signed-off-by: Takao Indoh <indou.takao@fujitsu.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>