cpu: clean up register_cpu func

This patch could reduce one branch in this function. Also
make the code more readble.

Signed-off-by: Alex Shi <[e-mail]>
Acked-by: Daniel Lezcano <[e-mail]>
To: [e-mail]
To: Greg Kroah-Hartman <[e-mail]>
Cc: [e-mail]
Cc: Ulf Hansson <[e-mail]>
Cc: Daniel Lezcano <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/cpu.c

···
 	if (cpu->hotpluggable)
 		cpu->dev.groups = hotplugable_cpu_attr_groups;
 	error = device_register(&cpu->dev);
-	if (!error)
-		per_cpu(cpu_sys_devices, num) = &cpu->dev;
-	if (!error)
-		register_cpu_under_node(num, cpu_to_node(num));
+	if (error)
+		return error;
 
-	return error;
+	per_cpu(cpu_sys_devices, num) = &cpu->dev;
+	register_cpu_under_node(num, cpu_to_node(num));
+
+	return 0;
 }
 
 struct device *get_cpu_device(unsigned cpu)