wifi: rtw88: pci: Use enum type for rtw_hw_queue_mapping() and ac_to_hwq

rtw_hw_queue_mapping() and ac_to_hwq[] hold values of type enum
rtw_tx_queue_type. Change their types to reflect this to make it easier
to understand this part of the code.

While here, also change the array to be static const as it is not
supposed to be modified at runtime.
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230204233001.1511643-2-martin.blumenstingl@googlemail.com

drivers/net/wireless/realtek/rtw88/pci.c

@@ -669,7 +669,7 @@ static void rtw_pci_deep_ps(struct rtw_dev *rtwdev, bool enter)
 	spin_unlock_bh(&rtwpci->irq_lock);
 }
 
-static u8 ac_to_hwq[] = {
+static const enum rtw_tx_queue_type ac_to_hwq[] = {
 	[IEEE80211_AC_VO] = RTW_TX_QUEUE_VO,
 	[IEEE80211_AC_VI] = RTW_TX_QUEUE_VI,
 	[IEEE80211_AC_BE] = RTW_TX_QUEUE_BE,
@@ -678,12 +678,12 @@ static u8 ac_to_hwq[] = {
 
 static_assert(ARRAY_SIZE(ac_to_hwq) == IEEE80211_NUM_ACS);
 
-static u8 rtw_hw_queue_mapping(struct sk_buff *skb)
+static enum rtw_tx_queue_type rtw_hw_queue_mapping(struct sk_buff *skb)
 {
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 	__le16 fc = hdr->frame_control;
 	u8 q_mapping = skb_get_queue_mapping(skb);
-	u8 queue;
+	enum rtw_tx_queue_type queue;
 
 	if (unlikely(ieee80211_is_beacon(fc)))
 		queue = RTW_TX_QUEUE_BCN;