mm/memcontrol.c: uninline mem_cgroup_usage

gcc version 5.2.1 20151010 (Debian 5.2.1-22)
$ size mm/memcontrol.o mm/memcontrol.o.before
   text    data     bss     dec     hex filename
  35535    7908      64   43507    a9f3 mm/memcontrol.o
  35762    7908      64   43734    aad6 mm/memcontrol.o.before

Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2801,7 +2801,7 @@ static unsigned long tree_stat(struct mem_cgroup *memcg,
 	return val;
 }
 
-static inline unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
+static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
 {
 	unsigned long val;