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/s2io.c b/drivers/net/s2io.c
index a032d72..22371f1 100644
--- a/drivers/net/s2io.c
+++ b/drivers/net/s2io.c
@@ -6692,7 +6692,7 @@
 	int changed = 0;
 
 	if (data & ~ETH_FLAG_LRO)
-		return -EOPNOTSUPP;
+		return -EINVAL;
 
 	if (data & ETH_FLAG_LRO) {
 		if (lro_enable) {