memcg: get rid of soft-limit tree infrastructure

memcg: get rid of soft-limit tree infrastructure

Now that the soft limit is integrated to the reclaim directly the whole
soft-limit tree infrastructure is not needed anymore.  Rip it out.

Signed-off-by: Michal Hocko <[email protected]>
Reviewed-by: Glauber Costa <[email protected]>
Reviewed-by: Tejun Heo <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Ying Han <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>