pch_uart: don't hardcode PCI slot to get DMA device

The DMA is a function 0 of the multifunction device where SPI host is attached.
Thus, we may avoid to hardcode PCI slot number.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/pch_uart.c

@@ -736,9 +736,10 @@ static void pch_request_dma(struct uart_port *port)
 	dma_cap_zero(mask);
 	dma_cap_set(DMA_SLAVE, mask);
 
-	dma_dev = pci_get_bus_and_slot(priv->pdev->bus->number,
-				       PCI_DEVFN(0xa, 0)); /* Get DMA's dev
-								information */
+	/* Get DMA's dev information */
+	dma_dev = pci_get_slot(priv->pdev->bus,
+			PCI_DEVFN(PCI_SLOT(priv->pdev->devfn), 0));
+
 	/* Set Tx DMA */
 	param = &priv->param_tx;
 	param->dma_dev = &dma_dev->dev;