mac80211: move TX info into skb->cb

This patch converts mac80211 and all drivers to have transmit
information and status in skb->cb rather than allocating extra
memory for it and copying all the data around. To make it fit,
a union is used where only data that is necessary for all steps
is kept outside of the union.

A number of fixes were done by Ivo, as well as the rt2x00 part
of this patch.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/b43.h

@@ -733,7 +733,6 @@ struct b43_wl {
 	/* The beacon we are currently using (AP or IBSS mode).
 	 * This beacon stuff is protected by the irq_lock. */
 	struct sk_buff *current_beacon;
-	struct ieee80211_tx_control beacon_txctl;
 	bool beacon0_uploaded;
 	bool beacon1_uploaded;
 	struct work_struct beacon_update_trigger;