netdev: Make ethtool_ops::set_flags() return -EINVAL for unsupported flags

The documented error code for attempts to set unsupported flags (or
to clear flags that cannot be disabled) is EINVAL, not EOPNOTSUPP.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Acked-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/netxen/netxen_nic_ethtool.c b/drivers/net/netxen/netxen_nic_ethtool.c
index 6d94ee5..b30de24 100644
--- a/drivers/net/netxen/netxen_nic_ethtool.c
+++ b/drivers/net/netxen/netxen_nic_ethtool.c
@@ -888,7 +888,7 @@
 	int hw_lro;
 
 	if (data & ~ETH_FLAG_LRO)
-		return -EOPNOTSUPP;
+		return -EINVAL;
 
 	if (!(adapter->capabilities & NX_FW_CAPABILITY_HW_LRO))
 		return -EINVAL;