This exports the workingset counters, i.e., workingset_refault,
workingset_activate, workingset_restore, and workingset_nodereclaim, to
memory cgroup v1.

The stat collection of these counters is shared between memory cgroup v1
and v2.  What this patch does is just to export them on memory cgroup v1.
Signed-off-by: NXu Yu <xuyu@linux.alibaba.com>
Reviewed-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>