driver core: test_async: fix up typo found by 0-day

0-day pointed out a typo in the platform device registration logic, so
fix it.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Dmitry Torokhov <dtor@chromium.org>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/test/test_async_driver_probe.c

@@ -116,7 +116,7 @@ static int __init test_async_probe_init(void)
 	calltime = ktime_get();
 	sync_dev_1 = platform_device_register_simple("test_sync_driver", 1,
 						     NULL, 0);
-	if (IS_ERR(async_dev_1)) {
+	if (IS_ERR(sync_dev_1)) {
 		error = PTR_ERR(sync_dev_1);
 		pr_err("failed to create sync_dev_1: %d", error);
 		goto err_unregister_sync_driver;