drivers: spi: driver reloading dma buffers in the main transceive loop

	LL_SPI_Enable(spi);

	do {

	} while (spi_stm32_dma_transfer_ongoing(data));

	/* store spi peripheral address */

	u32_t periph_addr = data->dma_tx.dma_cfg.head_block->dest_address;

	for (; ;) {

		/* wait for SPI busy flag */

		while (LL_SPI_IsActiveFlag_BSY(spi) == 1) {

		}

		/* once SPI is no more busy, wait for DMA transfer end */

		while (spi_stm32_dma_transfer_ongoing(data) == 1) {

		}

		if ((data->ctx.tx_count <= 1) && (data->ctx.rx_count <= 1)) {

			/* if it was the last count, then we are done */

			break;

		}

		if (data->dma_tx.transfer_complete == true) {

			LL_SPI_DisableDMAReq_TX(spi);

			/*

			 * Update the current Tx buffer, decreasing length of

			 * data->ctx.tx_count,  by its own length

			 */

			spi_context_update_tx(&data->ctx, 1, data->ctx.tx_len);

			/* keep the same dest (peripheral) */

			data->dma_tx.transfer_complete = false;

			/* and reload dma with a new source (memory) buffer */

			dma_reload(data->dev_dma_tx,

				data->dma_tx.channel,

				(u32_t)data->ctx.tx_buf,

				periph_addr,

				data->ctx.tx_len);

		}

		if (data->dma_rx.transfer_complete == true) {

			LL_SPI_DisableDMAReq_RX(spi);

			/*

			 * Update the current Rx buffer, decreasing length of

			 * data->ctx.rx_count,  by its own length

			 */

			spi_context_update_rx(&data->ctx, 1, data->ctx.rx_len);

			/* keep the same source (peripheral) */

			data->dma_rx.transfer_complete = false;

			/* and reload dma with a new dest (memory) buffer */

			dma_reload(data->dev_dma_rx,

				data->dma_rx.channel,

				periph_addr,

				(u32_t)data->ctx.rx_buf,

				data->ctx.rx_len);

		}

		LL_SPI_EnableDMAReq_RX(spi);

		LL_SPI_EnableDMAReq_TX(spi);

	}

	/* end of the transfer : all buffers sent/receceived */

	LL_SPI_Disable(spi);

	/* This is turned off in spi_stm32_complete(). */

	spi_context_cs_control(&data->ctx, true);