net/fec: fix the .remove code

net/fec: fix the .remove code

The .remove code is broken in several ways.
 - mdiobus_unregister() is called twice for the same object in case of dual FEC
 - phy_disconnect() is being called when the PHY is already disconnected
 - the requested IRQ(s) are not freed
 - fec_stop() is being called with the inteface already stopped

 All of those lead to kernel crashes if the remove function is actually used.

Signed-off-by: Lothar Waßmann <[email protected]>
Tested-by: Shawn Guo <[email protected]>
Acked-by: Shawn Guo <[email protected]>
Signed-off-by: David S. Miller <[email protected]>