cpu: Remove new instance of __cpuinit that crept back in

We removed __cpuinit support (leaving no-op stubs) quite some time ago.
However a new instance was added in commit 00df35f991
("cpu: Defer smpboot kthread unparking until CPU known to scheduler")

Since we want to clobber the stubs soon, get this removed now.

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/cpu.c

@@ -479,7 +479,7 @@ static struct notifier_block smpboot_thread_notifier = {
 	.priority = CPU_PRI_SMPBOOT,
 };
 
-void __cpuinit smpboot_thread_init(void)
+void smpboot_thread_init(void)
 {
 	register_cpu_notifier(&smpboot_thread_notifier);
 }