qcacld-3.0: Use IE length to determine if that IE is present

Propagate from qcacld-2.0 to qcacld-3.0

In limPerformFTPreAuth(), ft_ies pointer itself is used to determine
whether FT IE is present which is incorrect way to determine. Use
ft_ies_length instead to determine whether FT IE is present.

Change-Id: I36329de0ae41c03383f193b43eea214aed2770ca
CRs-Fixed: 979671

core/mac/src/pe/lim/lim_ft_preauth.c

@@ -237,7 +237,8 @@ void lim_perform_ft_pre_auth(tpAniSirGlobal pMac, QDF_STATUS status,
 	if (psessionEntry->is11Rconnection &&
 	    psessionEntry->ftPEContext.pFTPreAuthReq) {
 		/* Only 11r assoc has FT IEs */
-		if (psessionEntry->ftPEContext.pFTPreAuthReq->ft_ies == NULL) {
+		if (psessionEntry->ftPEContext.pFTPreAuthReq->ft_ies_length
+									== 0) {
 			lim_log(pMac, LOGE,
 				FL("FTIEs for Auth Req Seq 1 is absent"));
 			goto preauth_fail;