mm/mm_init.c: use hotplug_memory_notifier() directly

Commit 76ae8474 ("Documentation: raise minimum supported version of
GCC to 5.1") updated the minimum gcc version to 5.1.  So the problem
mentioned in f02c6968 ("include/linux/memory.h: implement
register_hotmemory_notifier()") no longer exist.  So we can now switch to
use hotplug_memory_notifier() directly rather than
register_hotmemory_notifier().

Link: https://lkml.kernel.org/r/20220923033347.3935160-6-liushixin2@huawei.comSigned-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Waiman Long <longman@redhat.com>
Cc: zefan li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mm_init.c

@@ -178,16 +178,10 @@ static int __meminit mm_compute_batch_notifier(struct notifier_block *self,
 	return NOTIFY_OK;
 }
 
-static struct notifier_block compute_batch_nb __meminitdata = {
-	.notifier_call = mm_compute_batch_notifier,
-	.priority = IPC_CALLBACK_PRI, /* use lowest priority */
-};
-
 static int __init mm_compute_batch_init(void)
 {
 	mm_compute_batch(sysctl_overcommit_memory);
-	register_hotmemory_notifier(&compute_batch_nb);
-
+	hotplug_memory_notifier(mm_compute_batch_notifier, IPC_CALLBACK_PRI);
 	return 0;
 }