cpu: Export cpu_up()

Building rcutorture as a module requires cpu_up() as well as cpu_down()
exported, so apply EXPORT_SYMBOL_GPL().

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/cpu.c

@@ -380,6 +380,7 @@ out:
 	cpu_maps_update_done();
 	return err;
 }
+EXPORT_SYMBOL_GPL(cpu_up);
 
 #ifdef CONFIG_PM_SLEEP_SMP
 static cpumask_var_t frozen_cpus;