driver core: test_async: fix an error code

The test_platform_device_register_node() function should return error
pointers instead of NULL. That is what the callers are expecting.

Fixes: 57ea974fb871 ("driver core: Rewrite test_async_driver_probe to cover serialization and NUMA affinity")
Signed-off-by: Dan Carpenter <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/test/test_async_driver_probe.c

···
 
 	pdev = platform_device_alloc(name, id);
 	if (!pdev)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	if (nid != NUMA_NO_NODE)
 		set_dev_node(&pdev->dev, nid);