rtlwifi: 8821a: btcoexist: add comments to explain why if-else branches are identical

The coexistence programmers preserve the same code of branches
intentionally to fine tune performance easier, because bandwidth and RSSI
strength are highly related to coexistence performance. The basic rule of
performance tuning is to assign most time slot to BT for realtime
application, and WiFi uses remaining time slot but don't lower than low
bound.
Reported-by: Inigo Huguet <ihuguet@redhat.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210506013738.5943-1-pkshih@realtek.com

drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8821a2ant.c

@@ -2810,6 +2810,7 @@ static void btc8821a2ant_action_a2dp(struct btc_coexist *btcoexist)
 					      0x4);
 	}
 
+	/* preserve identical branches for further fine-tuning */
 	if ((bt_rssi_state == BTC_RSSI_STATE_HIGH) ||
 	    (bt_rssi_state == BTC_RSSI_STATE_STAY_HIGH)) {
 		btc8821a2ant_ps_tdma(btcoexist, NORMAL_EXEC, true, 23);
@@ -2944,6 +2945,7 @@ static void btc8821a2ant_action_pan_edr(struct btc_coexist *btcoexist)
 					      0x4);
 	}
 
+	/* preserve identical branches for further fine-tuning */
 	if ((bt_rssi_state == BTC_RSSI_STATE_HIGH) ||
 	    (bt_rssi_state == BTC_RSSI_STATE_STAY_HIGH))
 		btc8821a2ant_ps_tdma(btcoexist, NORMAL_EXEC, true, 26);
@@ -3132,6 +3134,7 @@ static void btc8821a2ant_action_pan_edr_hid(struct btc_coexist *btcoexist)
 
 	btcoexist->btc_get(btcoexist, BTC_GET_U4_WIFI_BW, &wifi_bw);
 
+	/* preserve identical branches for further fine-tuning */
 	if (wifi_bw == BTC_WIFI_BW_LEGACY) {
 		/* for HID at 11b/g mode */
 		btc8821a2ant_coex_table(btcoexist, NORMAL_EXEC, 0x55ff55ff,
@@ -3321,6 +3324,7 @@ static void btc8821a2ant_action_hid_a2dp(struct btc_coexist *btcoexist)
 					      0x4);
 	}
 
+	/* preserve identical branches for further fine-tuning */
 	if ((bt_rssi_state == BTC_RSSI_STATE_HIGH) ||
 	    (bt_rssi_state == BTC_RSSI_STATE_STAY_HIGH)) {
 		btc8821a2ant_ps_tdma(btcoexist, NORMAL_EXEC, true, 23);