docs: fix all doxygen warnings

Doxygen warnings would previously not result in a failed pipeline.
Fixed this as well as all current warnings.

components/touch_element/include/touch_element/touch_matrix.h

@@ -1,16 +1,8 @@
-// Copyright 2016-2020 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: 2016-2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
 #pragma once
 
@@ -96,8 +88,6 @@ esp_err_t touch_matrix_install(const touch_matrix_global_config_t *global_config
 /**
  * @brief   Release resources allocated using touch_matrix_install()
  *
- * @return
- *      - ESP_OK: Successfully released resources
  */
 void touch_matrix_uninstall(void);