share_pool: Add VM_SHARE_POOL flag for vm_area_struct

ascend inclusion
category: Feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4NDAW


CVE: NA

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

This flag specify that the vm_area_struct is related to share_pool (in
detail, has a spa corresponding to it).

Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>
Signed-off-by: Tang Yizhou <tangyizhou@huawei.com>
Reviewed-by: Kefeng <Wang&lt;wangkefeng.wang@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>