wifi: rtw88: correct qsel_to_ep[] type as int

qsel_to_ep[] can be assigned negative value, so change type from 'u8' to
'int'. Otherwise, Smatch static checker warns:
  drivers/net/wireless/realtek/rtw88/usb.c:219 rtw_usb_parse() warn:
  assigning (-22) to unsigned variable 'rtwusb->qsel_to_ep[8]'

Cc: stable@vger.kernel.org
Fixes: a6f187f9 ("wifi: rtw88: usb: fix priority queue to endpoint mapping")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/linux-wireless/c3f70197-829d-48ed-ae15-66a9de80fa90@kili.mountain/
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230508085539.46795-1-pkshih@realtek.com

drivers/net/wireless/realtek/rtw88/usb.h

@@ -78,7 +78,7 @@ struct rtw_usb {
 	u8 pipe_interrupt;
 	u8 pipe_in;
 	u8 out_ep[RTW_USB_EP_MAX];
-	u8 qsel_to_ep[TX_DESC_QSEL_MAX];
+	int qsel_to_ep[TX_DESC_QSEL_MAX];
 	u8 usb_txagg_num;
 
 	struct workqueue_struct *txwq, *rxwq;