net: sh-eth: Fix build error by the value which is not defined

```--
drivers/net/ethernet/renesas/sh_eth.c:1706: error: 'pdid' undeclared (first use in this function)
drivers/net/ethernet/renesas/sh_eth.c:1706: error: (Each undeclared identifier is reported only once
drivers/net/ethernet/renesas/sh_eth.c:1706: error: for each function it appears in.)
make[5]: *** [drivers/net/ethernet/renesas/sh_eth.o] Error 1
```

--
Signed-off-by: NNobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
CC: Florian Fainelli <florian@openwrt.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/sh_eth.c

@@ -1703,7 +1703,7 @@ static int sh_mdio_init(struct net_device *ndev, int id,
 	mdp->mii_bus->name = "sh_mii";
 	mdp->mii_bus->parent = &ndev->dev;
 	snprintf(mdp->mii_bus->id, MII_BUS_ID_SIZE, "%s-%x",
-		mdp->pdev->name, pdid);
+		mdp->pdev->name, id);
 
 	/* PHY IRQ */
 	mdp->mii_bus->irq = kmalloc(sizeof(int)*PHY_MAX_ADDR, GFP_KERNEL);