sky2: fix checksum bit management on some chips

The newer flavors of Yukon II use a different method for receive
checksum offload. This is indicated in the driver by the SKY2_HW_NEW_LE
flag. On these newer chips, the BMU_ENA_RX_CHKSUM should not be set.

The driver would get incorrectly toggle the bit, enabling the old
checksum logic on these chips and cause a BUG_ON() assertion. If
receive checksum was toggled via ethtool.

Reported-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/sky2.c

@@ -4381,10 +4381,12 @@ static int sky2_set_features(struct net_device *dev, netdev_features_t features)
 	struct sky2_port *sky2 = netdev_priv(dev);
 	netdev_features_t changed = dev->features ^ features;
 
-	if (changed & NETIF_F_RXCSUM) {
-		bool on = features & NETIF_F_RXCSUM;
-		sky2_write32(sky2->hw, Q_ADDR(rxqaddr[sky2->port], Q_CSR),
-			     on ? BMU_ENA_RX_CHKSUM : BMU_DIS_RX_CHKSUM);
+	if ((changed & NETIF_F_RXCSUM) &&
+	    !(sky2->hw->flags & SKY2_HW_NEW_LE)) {
+		sky2_write32(sky2->hw,
+			     Q_ADDR(rxqaddr[sky2->port], Q_CSR),
+			     (features & NETIF_F_RXCSUM)
+			     ? BMU_ENA_RX_CHKSUM : BMU_DIS_RX_CHKSUM);
 	}
 
 	if (changed & NETIF_F_RXHASH)