mm/rmap: Fix kabi broken in anon_vma

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5USOP


CVE: CVE-2022-42703

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

In order to fix CVE-2022-42703, degree in struct anon_vma is splited into
two variables(num_children, num_active_vmas) and this will lead to broken
kabi.

Since struct anon_vma is only used by mm module and referenced by other
struct as pointers. So we can ignore this kabi change warning.

For variable degree in struct anon_vma, previous patch has already
delete this but this will lead to kabi change. Add it back at the same
position. For variables(num_children, num_active_vmas), put them
between macro __GENKSYMS__.

Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>