iwlwifi: mvm: don't send SMPS action frame with single RX antenna

Products that have only 1 antenna in Rx don't support MIMO
in RX. As a consequence, they will be in STATIC always.
Don't tell mac80211 to update SMPS in that case. mac80211
would send an action frame to the AP which is clearly
bogus.
As a matter of fact, we have seen that some APs send a
deauth when that happens.
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/utils.c

@@ -518,6 +518,11 @@ void iwl_mvm_update_smps(struct iwl_mvm *mvm, struct ieee80211_vif *vif,
 	int i;
 
 	lockdep_assert_held(&mvm->mutex);
+
+	/* SMPS is irrelevant for NICs that don't have at least 2 RX antenna */
+	if (num_of_ant(iwl_fw_valid_rx_ant(mvm->fw)) == 1)
+		return;
+
 	mvmvif = iwl_mvm_vif_from_mac80211(vif);
 	mvmvif->smps_requests[req_type] = smps_request;
 	for (i = 0; i < NUM_IWL_MVM_SMPS_REQ; i++) {