xen/pcpu: fix possible memory leak in register_pcpu()

In device_add(), dev_set_name() is called to allocate name, if it returns
error, the name need be freed. As comment of device_register() says, it
should use put_device() to give up the reference in the error path. So fix
this by calling put_device(), then the name can be freed in kobject_cleanup().

Fixes: f65c9bb3 ("xen/pcpu: Xen physical cpus online/offline sys interface")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20221110152441.401630-1-yangyingliang@huawei.comSigned-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/pcpu.c

@@ -228,7 +228,7 @@ static int register_pcpu(struct pcpu *pcpu)
 
 	err = device_register(dev);
 	if (err) {
-		pcpu_release(dev);
+		put_device(dev);
 		return err;
 	}