fs/proc/kcore.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/20220923033347.3935160-3-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>

fs/proc/kcore.c

@@ -18,7 +18,6 @@
 #include <linux/capability.h>
 #include <linux/elf.h>
 #include <linux/elfcore.h>
-#include <linux/notifier.h>
 #include <linux/vmalloc.h>
 #include <linux/highmem.h>
 #include <linux/printk.h>
@@ -638,10 +637,6 @@ static int __meminit kcore_callback(struct notifier_block *self,
 	return NOTIFY_OK;
 }
 
-static struct notifier_block kcore_callback_nb __meminitdata = {
-	.notifier_call = kcore_callback,
-	.priority = 0,
-};
 
 static struct kcore_list kcore_vmalloc;
 
@@ -694,7 +689,7 @@ static int __init proc_kcore_init(void)
 	add_modules_range();
 	/* Store direct-map area from physical memory map */
 	kcore_update_ram();
-	register_hotmemory_notifier(&kcore_callback_nb);
+	hotplug_memory_notifier(kcore_callback, 0);
 
 	return 0;
 }