[ETHTOOL]: Check correct pointer in ethtool_set_coalesce().

It was checking the "GET" function pointer instead of
the "SET" one.  Looks like a cut&paste error :-)
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/ethtool.c

@@ -356,7 +356,7 @@ static int ethtool_set_coalesce(struct net_device *dev, void __user *useraddr)
 {
 	struct ethtool_coalesce coalesce;
 
-	if (!dev->ethtool_ops->get_coalesce)
+	if (!dev->ethtool_ops->set_coalesce)
 		return -EOPNOTSUPP;
 
 	if (copy_from_user(&coalesce, useraddr, sizeof(coalesce)))