staging: wfx: fix BA sessions for older firmwares

Firmwares with API < 3.6 do not forward DELBA requests. Thus, when a
Block Ack session is restarted, the reordering buffer is not flushed and
the received sequence number is not contiguous. Therefore, mac80211
starts to wait some missing frames that it will never receive.

This patch disables the reordering buffer for old firmware. It is
harmless when the network is unencrypted. When the network is encrypted,
the non-contiguous frames will be thrown away by the TKIP/CCMP replay
protection. So, the user will observe some packet loss with UDP and
performance drop with TCP.

Fixes: e5da5fbd ("staging: wfx: fix CCMP/TKIP replay protection")
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20201007101943.749898-4-Jerome.Pouiller@silabs.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/data_rx.c

@@ -17,6 +17,9 @@ static void wfx_rx_handle_ba(struct wfx_vif *wvif, struct ieee80211_mgmt *mgmt)
 {
 	int params, tid;
 
+	if (wfx_api_older_than(wvif->wdev, 3, 6))
+		return;
+
 	switch (mgmt->u.action.u.addba_req.action_code) {
 	case WLAN_ACTION_ADDBA_REQ:
 		params = le16_to_cpu(mgmt->u.action.u.addba_req.capab);