mm: memory_hotplug: no need to check res twice in add_memory

Remove one redundant check of res.
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -901,7 +901,6 @@ int __ref add_memory(int nid, u64 start, u64 size)
 	/* rollback pgdat allocation and others */
 	if (new_pgdat)
 		rollback_node_hotadd(nid, pgdat);
-	if (res)
 	release_memory_resource(res);
 
 out: