iwlwifi: mvm: don't send fetch the TID from a non-QoS packet in TSO

Getting the TID of a packet before we know it is a QoS data
packet isn't a good idea. Delay the TID retrieval until
we know the packet is a QoS data packet.

Fixes: bb81bb68 ("iwlwifi: mvm: add Tx A-MSDU inside A-MPDU")
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/tx.c

@@ -715,11 +715,6 @@ static int iwl_mvm_tx_tso(struct iwl_mvm *mvm, struct sk_buff *skb,
 	snap_ip_tcp = 8 + skb_transport_header(skb) - skb_network_header(skb) +
 		tcp_hdrlen(skb);
 
-	qc = ieee80211_get_qos_ctl(hdr);
-	tid = *qc & IEEE80211_QOS_CTL_TID_MASK;
-	if (WARN_ON_ONCE(tid >= IWL_MAX_TID_COUNT))
-		return -EINVAL;
-
 	dbg_max_amsdu_len = ACCESS_ONCE(mvm->max_amsdu_len);
 
 	if (!sta->max_amsdu_len ||
@@ -730,6 +725,11 @@ static int iwl_mvm_tx_tso(struct iwl_mvm *mvm, struct sk_buff *skb,
 		goto segment;
 	}
 
+	qc = ieee80211_get_qos_ctl(hdr);
+	tid = *qc & IEEE80211_QOS_CTL_TID_MASK;
+	if (WARN_ON_ONCE(tid >= IWL_MAX_TID_COUNT))
+		return -EINVAL;
+
 	/*
 	 * Do not build AMSDU for IPv6 with extension headers.
 	 * ask stack to segment and checkum the generated MPDUs for us.