drivers: spi_mcux_lpspi: Clean up next_packet func

	struct spi_mcux_data *data = dev->data;

	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);

	struct spi_context *ctx = &data->ctx;

	size_t max_chunk = spi_context_max_continuous_chunk(ctx);

	lpspi_transfer_t transfer;

	status_t status;

	if ((ctx->tx_len == 0) && (ctx->rx_len == 0)) {

		/* nothing left to rx or tx, we're done! */

		spi_context_cs_control(&data->ctx, false);

		spi_context_complete(&data->ctx, dev, 0);

	if (max_chunk == 0) {

		spi_context_cs_control(ctx, false);

		spi_context_complete(ctx, dev, 0);

		return 0;

	}

	data->transfer_len = max_chunk;

	transfer.configFlags =

		kLPSPI_MasterPcsContinuous | (ctx->config->slave << LPSPI_MASTER_PCS_SHIFT);

	if (ctx->tx_len == 0) {

		/* rx only, nothing to tx */

		transfer.txData = NULL;

		transfer.rxData = ctx->rx_buf;

		transfer.dataSize = ctx->rx_len;

	} else if (ctx->rx_len == 0) {

		/* tx only, nothing to rx */

		transfer.txData = (uint8_t *)ctx->tx_buf;

		transfer.rxData = NULL;

		transfer.dataSize = ctx->tx_len;

	} else if (ctx->tx_len == ctx->rx_len) {

		/* rx and tx are the same length */

		transfer.txData = (uint8_t *)ctx->tx_buf;

		transfer.rxData = ctx->rx_buf;

		transfer.dataSize = ctx->tx_len;

	} else if (ctx->tx_len > ctx->rx_len) {

		/* Break up the tx into multiple transfers so we don't have to

		 * rx into a longer intermediate buffer. Leave chip select

		 * active between transfers.

		 */

		transfer.txData = (uint8_t *)ctx->tx_buf;

		transfer.rxData = ctx->rx_buf;

		transfer.dataSize = ctx->rx_len;

	} else {

		/* Break up the rx into multiple transfers so we don't have to

		 * tx from a longer intermediate buffer. Leave chip select

		 * active between transfers.

		 */

		transfer.txData = (uint8_t *)ctx->tx_buf;

		transfer.rxData = ctx->rx_buf;

		transfer.dataSize = ctx->tx_len;

	}

	data->transfer_len = transfer.dataSize;

	transfer.txData = (ctx->tx_len == 0 ? NULL : ctx->tx_buf);

	transfer.rxData = (ctx->rx_len == 0 ? NULL : ctx->rx_buf);

	transfer.dataSize = max_chunk;

	status = LPSPI_MasterTransferNonBlocking(base, &data->handle, &transfer);

	if (status != kStatus_Success) {