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/b43legacy/xmit.h

@@ -80,7 +80,7 @@ int b43legacy_generate_txhdr(struct b43legacy_wldev *dev,
 			      u8 *txhdr,
 			      const unsigned char *fragment_data,
 			      unsigned int fragment_len,
-			      const struct ieee80211_tx_control *txctl,
+			      const struct ieee80211_tx_info *info,
 			      u16 cookie);