i2s_event_data_t struct

The first level pointer of DMA buffer that just finished sending or receiving for `on_recv` and `on_sent` callback NULL for `on_recv_q_ovf` and `on_send_q_ovf` callback.

The buffer size of DMA buffer when success to send or receive, also the buffer size that dropped when queue overflow. It is related to the dma_frame_num and data_bit_width, typically it is fixed when data_bit_width is not changed.