Use common names from vmstat array when possible.  This gives not much
difference in code size for now, but should help in keeping interfaces
consistent.

  add/remove: 0/2 grow/shrink: 2/0 up/down: 70/-72 (-2)
  Function                                     old     new   delta
  memory_stat_format                           984    1050     +66
  memcg_stat_show                              957     961      +4
  memcg1_event_names                            32       -     -32
  mem_cgroup_lru_names                          40       -     -40
  Total: Before=14485337, After=14485335, chg -0.00%

Link: http://lkml.kernel.org/r/157113012508.453.80391533767219371.stgit@buzzSigned-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>