qcacld-3.0: Fix Wlan Tx failed when bt-coex for Rome

Current gTxChainMask1ss is 1 by default, only chain 1 can be used
by wifi when bt co-ex, if only chain0 exist or green AP switch to
1x1 mode, wifi tx will fail, connect will fail.

Add clear comment for gTxChainMask1ss to avoid confusing.
gTxChainMask1ss is only used by Rome, not by Helium and HST.

NOTE WELL: This change will have an adverse impact on products
which implicitly expect gTxChainMask1ss=1 behavior. Any such
products must update their INI file to add an explicit
"gTxChainMask1ss=1" entry.

Change-Id: I44f34f80200d057188a77f6f564a13c768fc727e
CRs-Fixed: 2426623

components/mlme/dispatcher/inc/cfg_mlme_chainmask.h

@@ -111,21 +111,33 @@
 
 /*
  * <ini>
- * gTxChainMask1ss - Enables/disables tx chain Mask1ss
+ * gTxChainMask1ss - Enables/disables tx chain mask1ss, used by Rome
  * @Min: 0
  * @Max: 3
- * @Default: 1
+ * @Default: 0
+ *
+ * This ini is used to set default tx chain mask for 1ss
+ *
+ * gTxChainMask1ss=0 : 1ss data tx chain mask set to 3 and self gen chain mask
+ *    set to 3. This is default setting of fw side. For 1x1 case, WIFI will
+ *    using chain0 to sent 1ss data and selfgen packets. 2x2 case, WIFI will
+ *    using chain0 and chain1 to sent 1ss data and selfgen packets.
  *
- * This ini is used to set default tx chain Mask for 1ss
+ * gTxChainMask1ss=1 : 1ss data tx chain mask set to 2 and self gen chain mask
+ *    set to 2. This setting can work only when 2x2 case, WIFI will use chain1
+ *    to sent 1ss data packets and selfgen packets, this can improve BTC
+ *    performance a little, but have side affect when chain0 and chain1 RSSI
+ *    is unbalance or green AP is enabled. So we recommend not using it.
  *
- * 0 - 3X3
- * 1 - 2X2
- * 2 - 3X2
- * 3 - 2X3
+ * gTxChainMask1ss=2 : 1ss data tx chain mask set to 3 and self gen chain mask
+ * set to 2. This setting never used before.
+ *
+ * gTxChainMask1ss=3 : 1ss data tx chain mask set to 2 and self gen chain mask
+ * set to 3. This setting never used before.
  *
  * Related: None
  *
- * Supported Feature: STA
+ * Supported Feature: STA/SAP
  *
  * Usage: Internal/External
  *
@@ -135,7 +147,7 @@
 			"gTxChainMask1ss", \
 			0, \
 			3, \
-			1, \
+			0, \
 			CFG_VALUE_OR_DEFAULT, \
 			"1SS Tx Chainmask")