iwlwifi: mvm: only save csa_vif in AP/GO mode

We only need the csa_vif in AP/GO modes, and assigning for other
interfaces may cause problems, because csa_vif is never cleared.  To
prevent this, only assign the value if the iftype is
NL80211_IFTYPE_AP.  Use a switch to do this, even though, for now,
only the AP interface type is handled, because soon other interface
types will be added as well.

Additionally, convert the WARN() in the error case when a
channel-switch is already running to WARN_ONCE().
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>

drivers/net/wireless/iwlwifi/mvm/mac80211.c

@@ -3110,17 +3110,25 @@ static int iwl_mvm_pre_channel_switch(struct ieee80211_hw *hw,
 
 	mutex_lock(&mvm->mutex);
 
-	csa_vif = rcu_dereference_protected(mvm->csa_vif,
-					    lockdep_is_held(&mvm->mutex));
-	if (WARN(csa_vif && csa_vif->csa_active,
-		 "Another CSA is already in progress")) {
-		ret = -EBUSY;
-		goto out_unlock;
-	}
-
-	IWL_DEBUG_MAC80211(mvm, "CSA started to freq %d\n",
+	IWL_DEBUG_MAC80211(mvm, "pre CSA to freq %d\n",
 			   chsw->chandef.center_freq1);
-	rcu_assign_pointer(mvm->csa_vif, vif);
+
+	switch (vif->type) {
+	case NL80211_IFTYPE_AP:
+		csa_vif =
+			rcu_dereference_protected(mvm->csa_vif,
+						  lockdep_is_held(&mvm->mutex));
+		if (WARN_ONCE(csa_vif && csa_vif->csa_active,
+			      "Another CSA is already in progress")) {
+			ret = -EBUSY;
+			goto out_unlock;
+		}
+
+		rcu_assign_pointer(mvm->csa_vif, vif);
+		break;
+	default:
+		break;
+	}
 
 	ret = 0;