net/designware: call phy_connect_dev() to properly setup phylib device

This sets up the linkage from the phydev back to the ethernet device. This
symptom of not doing this which I noticed was:
    <NULL> Waiting for PHY auto negotiation to complete....
rather than:
    dwmac.1c50000 Waiting for PHY auto negotiation to complete....
Signed-off-by: NIan Campbell <ijc@hellion.org.uk>
Cc: Alexey Brodkin <Alexey.Brodkin@synopsys.com>

drivers/net/designware.c

@@ -390,6 +390,8 @@ static int dw_phy_init(struct eth_device *dev)
 	if (!phydev)
 		return -1;
 
+	phy_connect_dev(phydev, dev);
+
 	phydev->supported &= PHY_GBIT_FEATURES;
 	phydev->advertising = phydev->supported;