mm: memcontrol: use the node-native slab memory counters

mm: memcontrol: use the node-native slab memory counters

Now that the slab counters are moved from the zone to the node level we
can drop the private memcg node stats and use the official ones.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Johannes Weiner <[email protected]>
Acked-by: Vladimir Davydov <[email protected]>
Cc: Josef Bacik <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Rik van Riel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>