mac80211: free up 2 bytes in skb->cb

Free up 2 bytes in skb->cb to be used for multi-rate retry later.
Move iv_len and icv_len initialization into key alloc.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2x00crypto.c b/drivers/net/wireless/rt2x00/rt2x00crypto.c
index e1448cf..5a858e5 100644
--- a/drivers/net/wireless/rt2x00/rt2x00crypto.c
+++ b/drivers/net/wireless/rt2x00/rt2x00crypto.c
@@ -56,10 +56,10 @@
 	 * note that these lengths should only be added when
 	 * mac80211 does not generate it.
 	 */
-	overhead += tx_info->control.icv_len;
+	overhead += key->icv_len;
 
 	if (!(key->flags & IEEE80211_KEY_FLAG_GENERATE_IV))
-		overhead += tx_info->control.iv_len;
+		overhead += key->iv_len;
 
 	if (!(key->flags & IEEE80211_KEY_FLAG_GENERATE_MMIC)) {
 		if (key->alg == ALG_TKIP)