mac80211: allow changing TX-related netdev features

mac80211: allow changing TX-related netdev features

Set ndev->hw_features as well as ndev->features to allow
changing the TX-related features with ethtool.

We cannot (yet) change RX-related features since that
requires telling the driver about it and we have no API
for that yet.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/20200131111300.891737-10-luca@coelho.fi
Signed-off-by: Johannes Berg <johannes.berg@intel.com>