staging: vt6655: mac80211 conversion: add new rx functions

vnt_receive_frame which replaces device_receive_frame

and vnt_rx_data which handles mac80211 rx data

structures ieee80211_hw, ieee80211_vif and variable rx_rate are added
in structure vnt_private

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>