mfd: rtsx: Declare that the DMA address limitation is 32bit explicitly

Realtek PCIe card reader only supports 32bit DMA.
This declaration can improve the readability.
Signed-off-by: Wei WANG <wei_wang@realsil.com.cn>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/rtsx_pcr.c

@@ -1029,6 +1029,10 @@ static int rtsx_pci_probe(struct pci_dev *pcidev,
 		pci_name(pcidev), (int)pcidev->vendor, (int)pcidev->device,
 		(int)pcidev->revision);
 
+	ret = pci_set_dma_mask(pcidev, DMA_BIT_MASK(32));
+	if (ret < 0)
+		return ret;
+
 	ret = pci_enable_device(pcidev);
 	if (ret)
 		return ret;