ath9k: clean up the aggregation tid queue

Use a sk_buff_head instead containing skbs instead of a list_head
containing ath_bufs. This makes it easier to decouple the aggregation
code from the ath_buf struct

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index d961f11..eb4cdef 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -206,6 +206,7 @@
 };
 
 struct ath_frame_info {
+	struct ath_buf *bf;
 	int framelen;
 	enum ath9k_key_type keytype;
 	u8 keyix;
@@ -235,7 +236,7 @@
 
 struct ath_atx_tid {
 	struct list_head list;
-	struct list_head buf_q;
+	struct sk_buff_head buf_q;
 	struct ath_node *an;
 	struct ath_atx_ac *ac;
 	unsigned long tx_buf[BITS_TO_LONGS(ATH_TID_MAX_BUFS)];