ptp: Fix pass zero to ERR_PTR() in ptp_clock_register

Fix smatch warning:

drivers/ptp/ptp_clock.c:298 ptp_clock_register() warn:
 passing zero to 'ERR_PTR'

'err' should be set while device_create_with_groups and
pps_register_source fails

Fixes: 85a66e55 ("ptp: create "pins" together with the rest of attributes")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_clock.c

@@ -252,8 +252,10 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	ptp->dev = device_create_with_groups(ptp_class, parent, ptp->devid,
 					     ptp, ptp->pin_attr_groups,
 					     "ptp%d", ptp->index);
-	if (IS_ERR(ptp->dev))
+	if (IS_ERR(ptp->dev)) {
+		err = PTR_ERR(ptp->dev);
 		goto no_device;
+	}
 
 	/* Register a new PPS source. */
 	if (info->pps) {
@@ -264,6 +266,7 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 		pps.owner = info->owner;
 		ptp->pps_source = pps_register_source(&pps, PTP_PPS_DEFAULTS);
 		if (!ptp->pps_source) {
+			err = -EINVAL;
 			pr_err("failed to register pps source\n");
 			goto no_pps;
 		}