ctc: replace PTR_RET with PTR_ERR_OR_ZERO

PTR_RET is deprecated. Do not recommend its usage anymore.
Use PTR_ERR_OR_ZERO instead.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/ctcm_main.c

@@ -1837,7 +1837,7 @@ static int __init ctcm_init(void)
 	if (ret)
 		goto out_err;
 	ctcm_root_dev = root_device_register("ctcm");
-	ret = PTR_RET(ctcm_root_dev);
+	ret = PTR_ERR_OR_ZERO(ctcm_root_dev);
 	if (ret)
 		goto register_err;
 	ret = ccw_driver_register(&ctcm_ccw_driver);