cfg80211: implement cfg80211_get_station cfg80211 API
Implement and export the new cfg80211_get_station() API.
This utility can be used by other kernel modules to obtain
detailed information about a given wireless station.
It will be in particular useful to batman-adv which will
implement a wireless rate based metric.
Signed-off-by: Antonio Quartulli <antonio@open-mesh.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com>