mac80211: move TX station pointer and restructure TX

Remove the control.sta pointer from ieee80211_tx_info to free up
sufficient space in the TX skb control buffer for the upcoming
Transmit Power Control (TPC).
Instead, the pointer is now on the stack in a new control struct
that is passed as a function parameter to the drivers' tx method.

Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de>
Signed-off-by: Alina Friedrichsen <x-alina@gmx.net>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
[reworded commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/libertas_tf/main.c

@@ -227,7 +227,9 @@ static void lbtf_free_adapter(struct lbtf_private *priv)
 	lbtf_deb_leave(LBTF_DEB_MAIN);
 }
 
-static void lbtf_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
+static void lbtf_op_tx(struct ieee80211_hw *hw,
+		       struct ieee80211_tx_control *control,
+		       struct sk_buff *skb)
 {
 	struct lbtf_private *priv = hw->priv;