block/blk-mq-cpu.c: use hotcpu_notifier()

Cleaner, reduces text size when cpu hotplug is disabled.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-mq-cpu.c

@@ -28,10 +28,6 @@ static int blk_mq_main_cpu_notify(struct notifier_block *self,
 	return NOTIFY_OK;
 }
 
-static struct notifier_block __cpuinitdata blk_mq_main_cpu_notifier = {
-	.notifier_call	= blk_mq_main_cpu_notify,
-};
-
 void blk_mq_register_cpu_notifier(struct blk_mq_cpu_notifier *notifier)
 {
 	BUG_ON(!notifier->notify);
@@ -58,5 +54,5 @@ void blk_mq_init_cpu_notifier(struct blk_mq_cpu_notifier *notifier,
 
 void __init blk_mq_cpu_init(void)
 {
-	register_hotcpu_notifier(&blk_mq_main_cpu_notifier);
+	hotcpu_notifier(blk_mq_main_cpu_notify, 0);
 }