This is the only place left where dev->features are directly
exposed to userspace.

I know checkpatch.pl complains about __ethtool_{get,set}_flags(), but
the code is easier to read this way.
Signed-off-by: NMichał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>