spi: dw: Make DMA request line assignments explicit for Intel Medfield

The 2afccbd2 ("spi: dw: Discard static DW DMA slave structures")
did a clean up of global variables, which is fine, but messed up with
the carefully provided information in the custom DMA slave structures.
There reader can find an assignment of the DMA request lines in use.

Partially revert the above mentioned commit to restore readability
and maintainability of the code.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200529183150.44149-1-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw-dma.c

@@ -61,10 +61,8 @@ static void dw_spi_dma_maxburst_init(struct dw_spi *dws)
 
 static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 {
-	struct dw_dma_slave slave = {
-		.src_id = 0,
-		.dst_id = 0
-	};
+	struct dw_dma_slave dma_tx = { .dst_id = 1 }, *tx = &dma_tx;
+	struct dw_dma_slave dma_rx = { .src_id = 0 }, *rx = &dma_rx;
 	struct pci_dev *dma_dev;
 	dma_cap_mask_t mask;
 
@@ -80,14 +78,14 @@ static int dw_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 	dma_cap_set(DMA_SLAVE, mask);
 
 	/* 1. Init rx channel */
-	slave.dma_dev = &dma_dev->dev;
-	dws->rxchan = dma_request_channel(mask, dw_spi_dma_chan_filter, &slave);
+	rx->dma_dev = &dma_dev->dev;
+	dws->rxchan = dma_request_channel(mask, dw_spi_dma_chan_filter, rx);
 	if (!dws->rxchan)
 		goto err_exit;
 
 	/* 2. Init tx channel */
-	slave.dst_id = 1;
-	dws->txchan = dma_request_channel(mask, dw_spi_dma_chan_filter, &slave);
+	tx->dma_dev = &dma_dev->dev;
+	dws->txchan = dma_request_channel(mask, dw_spi_dma_chan_filter, tx);
 	if (!dws->txchan)
 		goto free_rxchan;