nl80211: Indicate driver-based offchannel TX on mgmt_tx_cancel_wait

Drivers that support frame transmission with mgmt_tx() may not support
driver-based offchannel TX. Use mgmt_tx_cancel_wait instead of mgmt_tx
when figuring out whether to indicate support for this with
NL80211_ATTR_OFFCHANNEL_TX_OK.
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/nl80211.c

@@ -871,8 +871,7 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 		NLA_PUT_U32(msg, NL80211_ATTR_MAX_REMAIN_ON_CHANNEL_DURATION,
 			    dev->wiphy.max_remain_on_channel_duration);
 
-	/* for now at least assume all drivers have it */
-	if (dev->ops->mgmt_tx)
+	if (dev->ops->mgmt_tx_cancel_wait)
 		NLA_PUT_FLAG(msg, NL80211_ATTR_OFFCHANNEL_TX_OK);
 
 	if (mgmt_stypes) {