component/bt: fix API typos, add license headers and fix some log messages

components/bt/bluedroid/api/include/esp_a2dp_api.h

@@ -1,3 +1,17 @@
+// Copyright 2015-2016 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.
+
 #ifndef __ESP_A2DP_API_H__
 #define __ESP_A2DP_API_H__
 
@@ -13,7 +27,7 @@
 typedef uint8_t esp_a2d_mct_t;
 
 /**
- * @brief Codec specific information for different codec types
+ * @brief Codec specific information elements as defined in A2DP spec.
  */
 
 /**
@@ -131,7 +145,7 @@ esp_err_t esp_a2d_register_callback(esp_profile_cb_t callback);
 
 /**
  * @brief           This function is called to register A2DP sink data output function
- *                  currently only supports SBC codec, and the output data is PCM format
+ *                  for now only supports SBC codec, and the output is PCM data stream
  *                  
  * @param[in]       callback: A2DP data callback function
  *