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>
diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index 8afb546..f991e8b 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -1287,7 +1287,9 @@
 /*
  * mac80211 handlers.
  */
-void rt2x00mac_tx(struct ieee80211_hw *hw, struct sk_buff *skb);
+void rt2x00mac_tx(struct ieee80211_hw *hw,
+		  struct ieee80211_tx_control *control,
+		  struct sk_buff *skb);
 int rt2x00mac_start(struct ieee80211_hw *hw);
 void rt2x00mac_stop(struct ieee80211_hw *hw);
 int rt2x00mac_add_interface(struct ieee80211_hw *hw,