wifi: ath9k: use proper statements in conditionals

A previous cleanup patch accidentally broke some conditional
expressions by replacing the safe "do {} while (0)" constructs
with empty macros. gcc points this out when extra warnings
are enabled:

drivers/net/wireless/ath/ath9k/hif_usb.c: In function 'ath9k_skb_queue_complete':
drivers/net/wireless/ath/ath9k/hif_usb.c:251:57: error: suggest braces around empty body in an 'else' statement [-Werror=empty-body]
  251 |                         TX_STAT_INC(hif_dev, skb_failed);

Make both sets of macros proper expressions again.

Fixes: d7fc7603 ("ath9k: htc: clean up statistics macros")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20221215165553.1950307-1-arnd@kernel.org

drivers/net/wireless/ath/ath9k/htc.h

@@ -327,9 +327,9 @@ static inline struct ath9k_htc_tx_ctl *HTC_SKB_CB(struct sk_buff *skb)
 }
 
 #ifdef CONFIG_ATH9K_HTC_DEBUGFS
-#define __STAT_SAFE(hif_dev, expr)	((hif_dev)->htc_handle->drv_priv ? (expr) : 0)
-#define CAB_STAT_INC(priv)		((priv)->debug.tx_stats.cab_queued++)
-#define TX_QSTAT_INC(priv, q)		((priv)->debug.tx_stats.queue_stats[q]++)
+#define __STAT_SAFE(hif_dev, expr)	do { ((hif_dev)->htc_handle->drv_priv ? (expr) : 0); } while (0)
+#define CAB_STAT_INC(priv)		do { ((priv)->debug.tx_stats.cab_queued++); } while (0)
+#define TX_QSTAT_INC(priv, q)		do { ((priv)->debug.tx_stats.queue_stats[q]++); } while (0)
 
 #define TX_STAT_INC(hif_dev, c) \
 		__STAT_SAFE((hif_dev), (hif_dev)->htc_handle->drv_priv->debug.tx_stats.c++)
@@ -378,10 +378,10 @@ void ath9k_htc_get_et_stats(struct ieee80211_hw *hw,
 			    struct ethtool_stats *stats, u64 *data);
 #else
 
-#define TX_STAT_INC(hif_dev, c)
-#define TX_STAT_ADD(hif_dev, c, a)
-#define RX_STAT_INC(hif_dev, c)
-#define RX_STAT_ADD(hif_dev, c, a)
+#define TX_STAT_INC(hif_dev, c)		do { } while (0)
+#define TX_STAT_ADD(hif_dev, c, a)	do { } while (0)
+#define RX_STAT_INC(hif_dev, c)		do { } while (0)
+#define RX_STAT_ADD(hif_dev, c, a)	do { } while (0)
 
 #define CAB_STAT_INC(priv)
 #define TX_QSTAT_INC(priv, c)