When backporting commit 0e4b01df8659 ("mm, memcg: throttle allocators
when failing reclaim over memory.high"), memory stall section was
inadvertently missing. Fix this issue by adding it back.

Fixes: eda29cc0 ("mm, memcg: throttle allocators when failing reclaim over memory.high")
Signed-off-by: NCaspar Zhang <caspar@linux.alibaba.com>
Acked-by: NJoseph Qi <joseph.qi@linux.alibaba.com>