wlan: Add support to fetch currently used antenna using ioctl

Add provision to fetch currently used antenna index with
an ioctl.

Change-Id: If46ca874138da690cc4a74bd980ac1e693f3686a
CRs-Fixed: 951762
diff --git a/CORE/SME/inc/sme_Api.h b/CORE/SME/inc/sme_Api.h
index d43f670..5fe1fa5 100644
--- a/CORE/SME/inc/sme_Api.h
+++ b/CORE/SME/inc/sme_Api.h
@@ -3842,5 +3842,8 @@
 eHalStatus sme_set_wificonfig_params(tHalHandle hHal, tSetWifiConfigParams *req);
 eHalStatus sme_getRegInfo(tHalHandle hHal, tANI_U8 chanId,
                           tANI_U32 *regInfo1, tANI_U32 *regInfo2);
+eHalStatus sme_GetCurrentAntennaIndex(tHalHandle hHal,
+                                      tCsrAntennaIndexCallback callback,
+                                      void *pContext, tANI_U8 sessionId);
 
 #endif //#if !defined( __SME_API_H )