enetc: fix return value for enetc_ioctl()

Return -EOPNOTSUPP instead of -EINVAL if the requested ioctl is not
implemented.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/enetc/enetc.c

@@ -1601,7 +1601,7 @@ int enetc_ioctl(struct net_device *ndev, struct ifreq *rq, int cmd)
 #endif
 
 	if (!ndev->phydev)
-		return -EINVAL;
+		return -EOPNOTSUPP;
 	return phy_mii_ioctl(ndev->phydev, rq, cmd);
 }