net: phy: Support set_loopback override

phy_read_status and various other PHY functions support PHY specific
overriding of driver functions by using a PHY specific pointer to the
PHY driver. Add support of PHY specific override to phy_loopback too.
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy_device.c

@@ -1821,11 +1821,10 @@ EXPORT_SYMBOL(phy_resume);
 
 int phy_loopback(struct phy_device *phydev, bool enable)
 {
-	struct phy_driver *phydrv = to_phy_driver(phydev->mdio.dev.driver);
 	int ret = 0;
 
-	if (!phydrv)
-		return -ENODEV;
+	if (!phydev->drv)
+		return -EIO;
 
 	mutex_lock(&phydev->lock);
 
@@ -1839,8 +1838,8 @@ int phy_loopback(struct phy_device *phydev, bool enable)
 		goto out;
 	}
 
-	if (phydrv->set_loopback)
-		ret = phydrv->set_loopback(phydev, enable);
+	if (phydev->drv->set_loopback)
+		ret = phydev->drv->set_loopback(phydev, enable);
 	else
 		ret = genphy_loopback(phydev, enable);