Stop phy code from returning success to unknown ioctls.

This kind of sucks, and prevents the Fedora installer from using the
device for network installs...

[root@efika phy]# iwconfig eth0
Warning: Driver for device eth0 has been compiled with an ancient version
of Wireless Extension, while this program support version 11 and later.
Some things may be broken...

eth0        ESSID:off/any  Nickname:""
          NWID:0  Channel:0  Access Point: 00:00:BF:81:14:E0
          Bit Rate:-1.08206e+06 kb/s   Sensitivity=0/0
          RTS thr:off   Fragment thr:off
          Encryption key:<too big>
          Power Management:off
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/net/phy/phy.c

@@ -406,6 +406,9 @@ int phy_mii_ioctl(struct phy_device *phydev,
 				&& phydev->drv->config_init)
 			phydev->drv->config_init(phydev);
 		break;
+
+	default:
+		return -ENOTTY;
 	}
 
 	return 0;