memcg: un-export __memcg_kmem_get_cache

It is only used in slab and should not be used anywhere else so there is
no need in exporting it.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -3513,7 +3513,6 @@ out:
 	rcu_read_unlock();
 	return cachep;
 }
-EXPORT_SYMBOL(__memcg_kmem_get_cache);
 
 /*
  * We need to verify if the allocation against current->mm->owner's memcg is