rmt: document and improve LL driver

components/soc/esp32s3/include/soc/rmt_reg.h

@@ -1,21 +1,12 @@
-/** Copyright 2021 Espressif Systems (Shanghai) PTE LTD
+/*
+ * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
  *
- *  Licensed under the Apache License, Version 2.0 (the "License");
- *  you may not use this file except in compliance with the License.
- *  You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- *  Unless required by applicable law or agreed to in writing, software
- *  distributed under the License is distributed on an "AS IS" BASIS,
- *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- *  See the License for the specific language governing permissions and
- *  limitations under the License.
+ * SPDX-License-Identifier: Apache-2.0
  */
 #pragma once
 
-#include <stdint.h>
 #include "soc/soc.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif