Encode EAP-Naks in expanded format if we got an expanded type request

Since methods defined by the IETF (vendor ID 0) could also be encoded in
expanded type format the previous check was insufficient.

src/libcharon/encoding/payloads/eap_payload.c

@@ -241,6 +241,12 @@ METHOD(eap_payload_t, get_type, eap_type_t,
 	return 0;
 }
 
+METHOD(eap_payload_t, is_expanded, bool,
+	private_eap_payload_t *this)
+{
+	return this->data.len > 4 ? this->data.ptr[4] == EAP_EXPANDED : FALSE;
+}
+
 METHOD2(payload_t, eap_payload_t, destroy, void,
 	private_eap_payload_t *this)
 {
@@ -272,6 +278,7 @@ eap_payload_t *eap_payload_create()
 			.get_code = _get_code,
 			.get_identifier = _get_identifier,
 			.get_type = _get_type,
+			.is_expanded = _is_expanded,
 			.destroy = _destroy,
 		},
 		.next_payload = NO_PAYLOAD,