qcacmn: Update correct Rx rate for SU Rx ppdu

Currently computation of Rx rate depends on SU MCS
and SU NSS for SU PPDU. For SU PPDU, incorrect SU NSS leads to
incorrect computation of Rx rate.
To fix this, use respective PPDU information(MCS and NSS) and
calculate Rx rate based on proper SU NSS.

Change-Id: I754a7ecd57ec02d33f211937b7ffd025278d1e05
CRs-Fixed: 2668760

dp/wifi3.0/dp_rx_mon_status.c

@@ -473,8 +473,11 @@ static inline void dp_rx_rate_stats_update(struct dp_peer *peer,
 		mcs = ppdu_user->mcs;
 
 	} else {
+		if (ppdu->u.nss == 0)
+			nss = 0;
+		else
+			nss = ppdu->u.nss - 1;
 		mcs = ppdu->u.mcs;
-		nss = ppdu->u.nss;
 	}
 
 	ratekbps = dp_getrateindex(ppdu->u.gi,