iwlwifi: publish Tx STBC support in VHT

If the device is MIMO and VHT capable it supports Tx STBC.
Unlike HT, any chip that supports VHT also support STBC so
no need for a config parameter.
Using num_of_ants multiple times warranted caching it.
Signed-off-by: Eyal Shapira <eyal@wizery.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/iwl-nvm-parse.c

@@ -263,7 +263,8 @@ static void iwl_init_vht_hw_capab(const struct iwl_cfg *cfg,
 				  struct iwl_nvm_data *data,
 				  struct ieee80211_sta_vht_cap *vht_cap)
 {
-	int bf_sts_cap = num_of_ant(data->valid_rx_ant) - 1;
+	int num_ants = num_of_ant(data->valid_rx_ant);
+	int bf_sts_cap = num_ants - 1;
 
 	vht_cap->vht_supported = true;
 
@@ -273,6 +274,9 @@ static void iwl_init_vht_hw_capab(const struct iwl_cfg *cfg,
 		       bf_sts_cap << IEEE80211_VHT_CAP_BEAMFORMEE_STS_SHIFT |
 		       7 << IEEE80211_VHT_CAP_MAX_A_MPDU_LENGTH_EXPONENT_SHIFT;
 
+	if (num_ants > 1)
+		vht_cap->cap |= IEEE80211_VHT_CAP_TXSTBC;
+
 	if (iwlwifi_mod_params.amsdu_size_8K)
 		vht_cap->cap |= IEEE80211_VHT_CAP_MAX_MPDU_LENGTH_7991;
 
@@ -286,7 +290,7 @@ static void iwl_init_vht_hw_capab(const struct iwl_cfg *cfg,
 			    IEEE80211_VHT_MCS_NOT_SUPPORTED << 12 |
 			    IEEE80211_VHT_MCS_NOT_SUPPORTED << 14);
 
-	if (num_of_ant(data->valid_rx_ant) == 1 ||
+	if (num_ants == 1 ||
 	    cfg->rx_with_siso_diversity) {
 		vht_cap->cap |= IEEE80211_VHT_CAP_RX_ANTENNA_PATTERN |
 				IEEE80211_VHT_CAP_TX_ANTENNA_PATTERN;