net: dsa: microchip: ptp: Fix error code in ksz_hwtstamp_set()

We want to return negative error codes here but the copy_to/from_user()
functions return the number of bytes remaining to be copied.

Fixes: c59e12a1 ("net: dsa: microchip: ptp: Initial hardware time stamping support")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/Y8fJxSvbl7UNVHh/@kiliSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/microchip/ksz_ptp.c

@@ -416,9 +416,8 @@ int ksz_hwtstamp_set(struct dsa_switch *ds, int port, struct ifreq *ifr)
 
 	prt = &dev->ports[port];
 
-	ret = copy_from_user(&config, ifr->ifr_data, sizeof(config));
-	if (ret)
-		return ret;
+	if (copy_from_user(&config, ifr->ifr_data, sizeof(config)))
+		return -EFAULT;
 
 	ret = ksz_set_hwtstamp_config(dev, prt, &config);
 	if (ret)
@@ -426,7 +425,10 @@ int ksz_hwtstamp_set(struct dsa_switch *ds, int port, struct ifreq *ifr)
 
 	memcpy(&prt->tstamp_config, &config, sizeof(config));
 
-	return copy_to_user(ifr->ifr_data, &config, sizeof(config));
+	if (copy_to_user(ifr->ifr_data, &config, sizeof(config)))
+		return -EFAULT;
+
+	return 0;
 }
 
 static ktime_t ksz_tstamp_reconstruct(struct ksz_device *dev, ktime_t tstamp)