!790 mm: enable ksm per process and cgroup

Merge Pull Request from: @sun_nanyong 
 
patch 1~6: backport mainline patchset（mm: process/cgroup ksm
support）and patches it depends on.
patch 7：Add control file "memory.ksm" to enable ksm per cgroup. 
 
Link:https://gitee.com/openeuler/kernel/pulls/790

 

Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>