1. fix the bug. Modify the condition that esp_bt_controller_mem_release() shoud be only called before esp_bt_controller_init() or after esp_bt_controller_deinit()
2. modify the example to use esp_bt_controller_mem_release()
- the first characteristic is used to receive data from client.
- the second characteristic is used to notify data to client.
- the third characteristic is used to receive command from client, user
can add code to process the command.
- the fourth characteristic is used to notify status to client.
- the fifth characteristic is used to keep ble connection
