wifi: rtw88: unlock on error path in rtw_ops_add_interface()

Call mutex_unlock(&rtwdev->mutex); before returning on this error path.

Fixes: f0e741e ("wifi: rtw88: add bitmap for dynamic port settings")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/ddd10a74-5982-4f65-8c59-c1cca558d239@kili.mountain

drivers/net/wireless/realtek/rtw88/mac80211.c

@@ -173,8 +173,10 @@ static int rtw_ops_add_interface(struct ieee80211_hw *hw,
 	mutex_lock(&rtwdev->mutex);
 
 	port = find_first_zero_bit(rtwdev->hw_port, RTW_PORT_NUM);
-	if (port >= RTW_PORT_NUM)
+	if (port >= RTW_PORT_NUM) {
+		mutex_unlock(&rtwdev->mutex);
 		return -EINVAL;
+	}
 	set_bit(port, rtwdev->hw_port);
 
 	rtwvif->port = port;