asix: do not free array priv->mdio->irq

Used to be allocated and required freeing, but now
priv->mdio->irq is now a fixed sized array and should no longer be
free'd.

Issue detected using static analysis with CoverityScan

Fixes: e7f4dc3536a400 ("mdio: Move allocation of interrupts into core")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/ax88172a.c

@@ -134,7 +134,6 @@ static void ax88172a_remove_mdio(struct usbnet *dev)
 
 	netdev_info(dev->net, "deregistering mdio bus %s\n", priv->mdio->id);
 	mdiobus_unregister(priv->mdio);
-	kfree(priv->mdio->irq);
 	mdiobus_free(priv->mdio);
 }