wifi: cw1200: remove RCU STA pointer handling in TX

We can call this in one of two ways: through mac80211, where
we're already in an RCU read-side critical section, or from
some other code in the driver where this pointer can only be
NULL. In any case, we get a 'free' already protected pointer
to the sta through info->control.sta, so we can use it on
the stack without any further protection.

Remove the rcu_dereference() and critical section.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220904212910.e5bc20dd17bf.Ib570ff7fde33c2b6eddef493a3541fa04eb47181@changeid

drivers/net/wireless/st/cw1200/txrx.c

@@ -762,8 +762,7 @@ void cw1200_tx(struct ieee80211_hw *dev,
 	if (ret)
 		goto drop;
 
-	rcu_read_lock();
-	sta = rcu_dereference(t.sta);
+	sta = t.sta;
 
 	spin_lock_bh(&priv->ps_state_lock);
 	{
@@ -776,8 +775,6 @@ void cw1200_tx(struct ieee80211_hw *dev,
 	if (tid_update && sta)
 		ieee80211_sta_set_buffered(sta, t.txpriv.tid, true);
 
-	rcu_read_unlock();
-
 	cw1200_bh_wakeup(priv);
 
 	return;