mm/memcontrol.c: replace cgroup_memory_nokmem with mem_cgroup_kmem_disabled()

mem_cgroup_kmem_disabled() checks whether the kmem accounting is off. 
Therefore, replace cgroup_memory_nokmem with mem_cgroup_kmem_disabled(),
which is the same work in percpu.c and slab_common.c.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Xiang Yang <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Souptick Joarder (HPE) <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Shakeel Butt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Xiang Yang

mm/memcontrol.c

@@ -3653,7 +3653,7 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
 {
 	struct obj_cgroup *objcg;
 
-	if (cgroup_memory_nokmem)
+	if (mem_cgroup_kmem_disabled())
 		return 0;
 
 	if (unlikely(mem_cgroup_is_root(memcg)))
@@ -3677,7 +3677,7 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup *parent;
 
-	if (cgroup_memory_nokmem)
+	if (mem_cgroup_kmem_disabled())
 		return;
 
 	if (unlikely(mem_cgroup_is_root(memcg)))