memcg: mark memcg1_events static const

memcg: mark memcg1_events static const

Mark memcg1_events static: it's only used by memcontrol.c.  And mark it
const: it's not modified.

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