gdma_get_alignment_constraints() function

- ESP_OK: Get alignment constraints successfully - ESP_ERR_INVALID_ARG: Get alignment constraints failed because of invalid argument - ESP_FAIL: Get alignment constraints failed because of other error

You should call this function after `gdma_config_transfer`, the later one can adjust the alignment constraints based on various conditions, e.g. burst size, memory encryption, etc. You can use returned alignment value to validate if a DMA buffer provided by the upper layer meets the constraints. The returned alignment doesn't take the cache line size into account, if you want to do aligned memory allocation, you should align the buffer size to the cache line size by yourself if the DMA buffer is behind a cache.