rcu: Add missing __cpuinit annotation in rcutorture code

"rcu: Add rcutorture CPU-hotplug capability" adds cpu hotplug operations
to the rcutorture code but produces a false positive warning about section
mismatches:

WARNING: vmlinux.o(.text+0x1e420c): Section mismatch in reference from the
	 function rcu_torture_onoff() to the function .cpuinit.text:cpu_up()
	 The function rcu_torture_onoff() references
	 the function __cpuinit cpu_up().
	 This is often because rcu_torture_onoff lacks a __cpuinit
	 annotation or the annotation of cpu_up is wrong.

This commit therefore adds a __cpuinit annotation so the warning goes away.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcutorture.c

@@ -1399,7 +1399,7 @@ rcu_torture_shutdown(void *arg)
  * Execute random CPU-hotplug operations at the interval specified
  * by the onoff_interval.
  */
-static int
+static int __cpuinit
 rcu_torture_onoff(void *arg)
 {
 	int cpu;
@@ -1447,7 +1447,7 @@ rcu_torture_onoff(void *arg)
 	return 0;
 }
 
-static int
+static int __cpuinit
 rcu_torture_onoff_init(void)
 {
 	if (onoff_interval <= 0)