iwlwifi: mvm: use helpers to get iwl_mvm_sta

Getting the mvm station out of station id requires dereferencing
the station id to get ieee80211_sta, then checking for pointer
validity and only then extract mvm station out.
Given that there are helpers to do it - use them instead of
duplicating the code whenever we need only mvm station.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/tt.c b/drivers/net/wireless/intel/iwlwifi/mvm/tt.c
index eb3f460..58fc7b3 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/tt.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/tt.c
@@ -359,16 +359,14 @@
 
 static void iwl_mvm_tt_tx_protection(struct iwl_mvm *mvm, bool enable)
 {
-	struct ieee80211_sta *sta;
 	struct iwl_mvm_sta *mvmsta;
 	int i, err;
 
 	for (i = 0; i < IWL_MVM_STATION_COUNT; i++) {
-		sta = rcu_dereference_protected(mvm->fw_id_to_mac_id[i],
-						lockdep_is_held(&mvm->mutex));
-		if (IS_ERR_OR_NULL(sta))
+		mvmsta = iwl_mvm_sta_from_staid_protected(mvm, i);
+		if (!mvmsta)
 			continue;
-		mvmsta = iwl_mvm_sta_from_mac80211(sta);
+
 		if (enable == mvmsta->tt_tx_protection)
 			continue;
 		err = iwl_mvm_tx_protection(mvm, mvmsta, enable);