esp8684: support GPIO peripheral, IO_MUX, GPIO matrix.

Generic GPIO example and GPIO unit test on esp8684 are both supported as well.

components/soc/esp32s2/gpio_periph.c

@@ -1,16 +1,8 @@
-// Copyright 2018 Espressif Systems (Shanghai) PTE 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-FileCopyrightText: 2018-2021 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
 #include "soc/gpio_periph.h"
 
@@ -62,7 +54,6 @@ const uint32_t GPIO_PIN_MUX_REG[SOC_GPIO_PIN_COUNT] = {
     IO_MUX_GPIO44_REG,
     IO_MUX_GPIO45_REG,
     IO_MUX_GPIO46_REG,
-    0,
 };
 
 const uint32_t GPIO_HOLD_MASK[SOC_GPIO_PIN_COUNT] = {
@@ -113,5 +104,4 @@ const uint32_t GPIO_HOLD_MASK[SOC_GPIO_PIN_COUNT] = {
     BIT(23),
     BIT(24),
     BIT(25),
-    BIT(26),
 };