memcontrol: use flexible-array member

Change deprecated zero-length-and-one-element-arrays into flexible array
member.Zero-length and one-element arrays detected by Lukas's CodeChecker.
Zero/one element arrays cause undefined behaviours if sizeof() used.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: wenhuizhang <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: Alexander Duyck <[email protected]>
Cc: Wei Yang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/memcontrol.h

@@ -349,8 +349,7 @@ struct mem_cgroup {
 	struct deferred_split deferred_split_queue;
 #endif
 
-	struct mem_cgroup_per_node *nodeinfo[0];
-	/* WARNING: nodeinfo must be the last member here */
+	struct mem_cgroup_per_node *nodeinfo[];
 };
 
 /*