wifi: rtw89: Disallow power save with multiple stations

Power saving for more than one station is not supported currently.
Disallow entering PS mode when we have more than one associated
stations.
Signed-off-by: Po-Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230415035016.15788-1-pkshih@realtek.com

drivers/net/wireless/realtek/rtw89/core.c

@@ -2509,6 +2509,9 @@ static void rtw89_vif_enter_lps(struct rtw89_dev *rtwdev, struct rtw89_vif *rtwv
 	    rtwvif->tdls_peer)
 		return;
 
+	if (rtwdev->total_sta_assoc > 1)
+		return;
+
 	if (rtwvif->offchan)
 		return;