ath10k: fix VHT NSS calculation when STBC is enabled

When STBC is enabled, NSTS_SU value need to be accounted for VHT NSS
calculation for SU case.

Without this fix, 1SS + STBC enabled case was reported wrongly as 2SS
in radiotap header on monitor mode capture.

Tested-on: QCA9984 10.4-3.10-00047
Signed-off-by: Sathishkumar Muruganandam <murugana@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1597392971-3897-1-git-send-email-murugana@codeaurora.org

drivers/net/wireless/ath/ath10k/htt_rx.c

@@ -949,6 +949,7 @@ static void ath10k_htt_rx_h_rates(struct ath10k *ar,
 	u8 preamble = 0;
 	u8 group_id;
 	u32 info1, info2, info3;
+	u32 stbc, nsts_su;
 
 	info1 = __le32_to_cpu(rxd->ppdu_start.info1);
 	info2 = __le32_to_cpu(rxd->ppdu_start.info2);
@@ -993,11 +994,16 @@ static void ath10k_htt_rx_h_rates(struct ath10k *ar,
 		 */
 		bw = info2 & 3;
 		sgi = info3 & 1;
+		stbc = (info2 >> 3) & 1;
 		group_id = (info2 >> 4) & 0x3F;
 
 		if (GROUP_ID_IS_SU_MIMO(group_id)) {
 			mcs = (info3 >> 4) & 0x0F;
-			nss = ((info2 >> 10) & 0x07) + 1;
+			nsts_su = ((info2 >> 10) & 0x07);
+			if (stbc)
+				nss = (nsts_su >> 2) + 1;
+			else
+				nss = (nsts_su + 1);
 		} else {
 			/* Hardware doesn't decode VHT-SIG-B into Rx descriptor
 			 * so it's impossible to decode MCS. Also since