rsi: parse TID from data frame correctly

Currently TID is extracted by checking at specific offset in data frame.
This approach doesn't work for some of the frames. This patch uses mac80211
API and do it correctly

Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Siva Rebbagondla <siva.rebbagondla@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/rsi/rsi_91x_core.c

@@ -432,7 +432,9 @@ void rsi_core_xmit(struct rsi_common *common, struct sk_buff *skb)
 		}
 	} else {
 		if (ieee80211_is_data_qos(wh->frame_control)) {
-			tid = (skb->data[24] & IEEE80211_QOS_TID);
+			u8 *qos = ieee80211_get_qos_ctl(wh);
+
+			tid = *qos & IEEE80211_QOS_CTL_TID_MASK;
 			skb->priority = TID_TO_WME_AC(tid);
 		} else {
 			tid = IEEE80211_NONQOS_TID;