drivers/base/node.c: switch to register_hotmemory_notifier()

Squishes a warning which my change to hotplug_memory_notifier() added.

I want to keep that warning, because it is punishment for failnig to check
the hotplug_memory_notifier() return value.

Cc: Greg KH <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/base/node.c

···
 #include <linux/mm.h>
 #include <linux/memory.h>
 #include <linux/vmstat.h>
+#include <linux/notifier.h>
 #include <linux/node.h>
 #include <linux/hugetlb.h>
 #include <linux/compaction.h>
···
 
 	ret = subsys_system_register(&node_subsys, cpu_root_attr_groups);
 	if (!ret) {
-		hotplug_memory_notifier(node_memory_callback,
-					NODE_CALLBACK_PRI);
+		static struct notifier_block node_memory_callback_nb = {
+			.notifier_call = node_memory_callback,
+			.priority = NODE_CALLBACK_PRI,
+		};
+		register_hotmemory_notifier(&node_memory_callback_nb);
 	}
 
 	/*