net: mvneta: Fix fault when wrong device tree

The driver does not check id phy_connect failed (for example on wrong
property name in device tree). In such a case a fault occurs and the
CPU is restarted.

Signed-off-by: Marek Behun <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>

drivers/net/mvneta.c

@@ -1562,6 +1562,10 @@ static int mvneta_start(struct udevice *dev)
 
 			phydev = phy_connect(pp->bus, pp->phyaddr, dev,
 					     pp->phy_interface);
+			if (!phydev) {
+				printf("phy_connect failed\n");
+				return -ENODEV;
+			}
 
 			pp->phydev = phydev;
 			phy_config(phydev);