ath9k: Fix sequence number assignment for non-data frames

Since commit 558ff225 (ath9k: fix
ps-poll responses under a-mpdu sessions) non-data frames would have
gotten a sequence number from a TIDs sequence counter instead of
using the global sequence counter.

This can lead to instable connections.

To fix this only select the correct TID if we are processing a
data frame. Furthermore, prevent non-data frames to get a sequence
number from a TID sequence counter by adding a check to
ath_tx_setup_buffer.

Cc: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/xmit.c

@@ -2063,7 +2063,7 @@ static struct ath_buf *ath_tx_setup_buffer(struct ath_softc *sc,
 
 	ATH_TXBUF_RESET(bf);
 
-	if (tid) {
+	if (tid && ieee80211_is_data_present(hdr->frame_control)) {
 		fragno = le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG;
 		seqno = tid->seq_next;
 		hdr->seq_ctrl = cpu_to_le16(tid->seq_next << IEEE80211_SEQ_SEQ_SHIFT);
@@ -2186,7 +2186,7 @@ int ath_tx_start(struct ieee80211_hw *hw, struct sk_buff *skb,
 		txq->stopped = true;
 	}
 
-	if (txctl->an)
+	if (txctl->an && ieee80211_is_data_present(hdr->frame_control))
 		tid = ath_get_skb_tid(sc, txctl->an, skb);
 
 	if (info->flags & IEEE80211_TX_CTL_PS_RESPONSE) {