staging: rtl8723au: Make rtw_cfg80211_add_wep() take a struct rtw_wep_key

This allows the removal of the ugly struct ndis_8802_11_wep and simplify
rtw_cfg80211_add_wep(). In addition remove unused element ndiswep from
struct security_priv.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>