r8169: improve rtl8169_init_ring

This function doesn't use the net_device, therefore change the
parameter to type struct rtl8169_private * to simplify the code.
In addition we don't need the calculations in the memset
statements, we can use the size of the arrays directly.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169.c

@@ -6803,14 +6803,12 @@ static int rtl8169_rx_fill(struct rtl8169_private *tp)
 	return -ENOMEM;
 }
 
-static int rtl8169_init_ring(struct net_device *dev)
+static int rtl8169_init_ring(struct rtl8169_private *tp)
 {
-	struct rtl8169_private *tp = netdev_priv(dev);
-
 	rtl8169_init_ring_indexes(tp);
 
-	memset(tp->tx_skb, 0x0, NUM_TX_DESC * sizeof(struct ring_info));
-	memset(tp->Rx_databuff, 0x0, NUM_RX_DESC * sizeof(void *));
+	memset(tp->tx_skb, 0, sizeof(tp->tx_skb));
+	memset(tp->Rx_databuff, 0, sizeof(tp->Rx_databuff));
 
 	return rtl8169_rx_fill(tp);
 }
@@ -7678,7 +7676,7 @@ static int rtl_open(struct net_device *dev)
 	if (!tp->RxDescArray)
 		goto err_free_tx_0;
 
-	retval = rtl8169_init_ring(dev);
+	retval = rtl8169_init_ring(tp);
 	if (retval < 0)
 		goto err_free_rx_1;