mm/memcontrol: use vmstat names for printing statistics

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@buzz


Signed-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>