net: fix hw_features ethtool_ops->set_flags compatibility

__ethtool_set_flags() was not taking into account features set but not
user-toggleable.

Since GFLAGS returns masked dev->features, EINVAL is returned when
passed flags differ to it, and not to wanted_features.

Signed-off-by: Michał Mirosław <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/ethtool.c

···
 	}
 
 	/* allow changing only bits set in hw_features */
-	changed = (data ^ dev->wanted_features) & flags_dup_features;
+	changed = (data ^ dev->features) & flags_dup_features;
 	if (changed & ~dev->hw_features)
 		return (changed & dev->hw_features) ? -EINVAL : -EOPNOTSUPP;
 
 	dev->wanted_features =
-		(dev->wanted_features & ~changed) | data;
+		(dev->wanted_features & ~changed) | (data & dev->hw_features);
 
 	__netdev_update_features(dev);