dac_continuous_write_cyclically() function

- ESP_ERR_INVALID_ARG The input parameter is invalid - ESP_ERR_INVALID_STATE The DAC continuous mode has not been enabled yet - ESP_OK Success to output the acyclic DAC data

The data in buffer will be converted cyclically using DMA once this function is called, This function will return once the data loaded into DMA buffers. The buffer size of cyclically output is limited by the descriptor number and dma buffer size while initializing the continuous mode. Concretely, in order to load all the data into descriptors, the cyclic buffer size is not supposed to be greater than `desc_num * buf_size` Specially, on ESP32, the data bit width of DAC continuous data is fixed to 16 bits while only the high 8 bits are available, The driver will help to expand the inputted buffer automatically by default, you can also align the data to 16 bits manually by clearing `CONFIG_DAC_DMA_AUTO_16BIT_ALIGN` in menuconfig.