BTA_GATTC_PrepareWriteCharDescr() function

* Function BTA_GATTC_PrepareWriteCharDescr * Description This function is called to prepare write a characteristic descriptor value. * Parameters conn_id - connection ID. * p_char_descr_id - GATT characteristic descriptor ID of the service. * offset - offset of the write value. * len: length of the data to be written. * p_value - the value to be written. * Returns None