net: microchip: lan743x: add fixed phy unregister support

When operating in fixed phy mode and if there is repeated open/close
phy test cases, everytime the fixed phy is registered as a new phy
which leads to overrun after 32 iterations. It is solved by adding
fixed_phy_unregister() in the phy_close path.

In phy_close path, netdev->phydev cannot be used directly in
fixed_phy_unregister() due to two reasons,
    - netdev->phydev is set to NULL in phy_disconnect()
    - fixed_phy_unregister() can be called only after phy_disconnect()
So saving the netdev->phydev in local variable 'phydev' and
passing it to phy_disconnect().

Signed-off-by: Pavithra Sathyanarayanan <Pavithra.Sathyanarayanan@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/lan743x_main.c

@@ -1466,9 +1466,15 @@ static void lan743x_phy_link_status_change(struct net_device *netdev)
 static void lan743x_phy_close(struct lan743x_adapter *adapter)
 {
 	struct net_device *netdev = adapter->netdev;
+	struct phy_device *phydev = netdev->phydev;
 
 	phy_stop(netdev->phydev);
 	phy_disconnect(netdev->phydev);
+
+	/* using phydev here as phy_disconnect NULLs netdev->phydev */
+	if (phy_is_pseudo_fixed_link(phydev))
+		fixed_phy_unregister(phydev);
+
 }
 
 static void lan743x_phy_interface_select(struct lan743x_adapter *adapter)