gpio_etm_task_add_gpio() function

- ESP_OK: Add GPIO to the ETM task successfully - ESP_ERR_INVALID_ARG: Add GPIO to the ETM task failed because of invalid argument, e.g. GPIO is not output capable, ETM task is not of GPIO type - ESP_ERR_INVALID_STATE: Add GPIO to the ETM task failed because the GPIO is used by other ETM task already - ESP_FAIL: Add GPIO to the ETM task failed because of other reasons

You can call this function multiple times to add more GPIOs Only GPIO ETM object can call this function