wlan: Set TxBF csn value based on ini configuration.

Broadcom AP has an issue that when pronto advertise the csn value
as 3 it uses the 2 antenna in the NDPA packet but it suppose to
use the 3 antenna in the NDPA packet. If we advertise the csn value
as 2 then it uses 3 antenna in the NDPA packet. We need to have
ini configuration for setting the csn value.

CRs-Fixed: 453491
Change-Id: I757a9dd5dbb5bf957f92253b9499802148302903
diff --git a/CORE/MAC/src/pe/lim/limSerDesUtils.c b/CORE/MAC/src/pe/lim/limSerDesUtils.c
index 85a6299..df45385 100644
--- a/CORE/MAC/src/pe/lim/limSerDesUtils.c
+++ b/CORE/MAC/src/pe/lim/limSerDesUtils.c
@@ -2043,6 +2043,12 @@
     if (limCheckRemainingLength(pMac, len) == eSIR_FAILURE)
         return eSIR_FAILURE;
 
+    //txBFCsnValue
+    pJoinReq->txBFCsnValue= *pBuf++;
+    len--;
+    if (limCheckRemainingLength(pMac, len) == eSIR_FAILURE)
+        return eSIR_FAILURE;
+
 #if (WNI_POLARIS_FW_PACKAGE == ADVANCED) && defined(ANI_PRODUCT_TYPE_AP)
     // Extract BP Indicator
     pJoinReq->bpIndicator = (tAniBool) limGetU32(pBuf);