mac80211: airtime: avoid variable shadowing

This isn't very dangerous, since the outer 'rate' variable
isn't even a pointer, but it's still confusing, so use a
different variable inside.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20220202104617.8e9b2bfaa0f5.I41c53f754eef28206d04dafc7263ccb99b63d490@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/airtime.c

 // SPDX-License-Identifier: ISC
 /*
  * Copyright (C) 2019 Felix Fietkau <nbd@nbd.name>
+ * Copyright (C) 2021 Intel Corporation
  */
 
 #include <net/mac80211.h>
@@ -650,12 +651,12 @@ u32 ieee80211_calc_expected_tx_airtime(struct ieee80211_hw *hw,
 		struct sta_info *sta = container_of(pubsta, struct sta_info,
 						    sta);
 		struct ieee80211_rx_status stat;
-		struct ieee80211_tx_rate *rate = &sta->tx_stats.last_rate;
+		struct ieee80211_tx_rate *tx_rate = &sta->tx_stats.last_rate;
 		struct rate_info *ri = &sta->tx_stats.last_rate_info;
 		u32 duration, overhead;
 		u8 agg_shift;
 
-		if (ieee80211_fill_rx_status(&stat, hw, rate, ri, band, len))
+		if (ieee80211_fill_rx_status(&stat, hw, tx_rate, ri, band, len))
 			return 0;
 
 		if (stat.encoding == RX_ENC_LEGACY || !ampdu)