spi/topcliff-pch: Fix DMA channel

bus_num might be asigned dynamically to e.g. 32766. In this case the
calculated DMA channel based on SPI bus number is bogus. Use SPI channel
number instead for calculation.
Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-topcliff-pch.c

@@ -915,7 +915,7 @@ static void pch_spi_request_dma(struct pch_spi_data *data, int bpw)
 	/* Set Tx DMA */
 	param = &dma->param_tx;
 	param->dma_dev = &dma_dev->dev;
-	param->chan_id = data->master->bus_num * 2; /* Tx = 0, 2 */
+	param->chan_id = data->ch * 2; /* Tx = 0, 2 */;
 	param->tx_reg = data->io_base_addr + PCH_SPDWR;
 	param->width = width;
 	chan = dma_request_channel(mask, pch_spi_filter, param);
@@ -930,7 +930,7 @@ static void pch_spi_request_dma(struct pch_spi_data *data, int bpw)
 	/* Set Rx DMA */
 	param = &dma->param_rx;
 	param->dma_dev = &dma_dev->dev;
-	param->chan_id = data->master->bus_num * 2 + 1; /* Rx = Tx + 1 */
+	param->chan_id = data->ch * 2 + 1; /* Rx = Tx + 1 */;
 	param->rx_reg = data->io_base_addr + PCH_SPDRR;
 	param->width = width;
 	chan = dma_request_channel(mask, pch_spi_filter, param);