drm/mgag200: Lookup VRAM PCI BAR start and length only once

The MM setup code on mgag200 reads PCI BAR 0's start and length
several times. Reusing these values makes the code more readable.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200605135803.19811-6-tzimmermann@suse.de

drivers/gpu/drm/mgag200/mgag200_mm.c

@@ -33,16 +33,18 @@
 int mgag200_mm_init(struct mga_device *mdev)
 {
 	struct drm_device *dev = mdev->dev;
+	resource_size_t start, len;
 	int ret;
 
-	arch_io_reserve_memtype_wc(pci_resource_start(dev->pdev, 0),
-				   pci_resource_len(dev->pdev, 0));
+	/* BAR 0 is VRAM */
+	start = pci_resource_start(dev->pdev, 0);
+	len = pci_resource_len(dev->pdev, 0);
 
-	mdev->fb_mtrr = arch_phys_wc_add(pci_resource_start(dev->pdev, 0),
-					 pci_resource_len(dev->pdev, 0));
+	arch_io_reserve_memtype_wc(start, len);
 
-	mdev->vram = ioremap(pci_resource_start(dev->pdev, 0),
-			     pci_resource_len(dev->pdev, 0));
+	mdev->fb_mtrr = arch_phys_wc_add(start, len);
+
+	mdev->vram = ioremap(start, len);
 	if (!mdev->vram) {
 		ret = -ENOMEM;
 		goto err_arch_phys_wc_del;
@@ -54,8 +56,7 @@ int mgag200_mm_init(struct mga_device *mdev)
 
 err_arch_phys_wc_del:
 	arch_phys_wc_del(mdev->fb_mtrr);
-	arch_io_free_memtype_wc(pci_resource_start(dev->pdev, 0),
-				pci_resource_len(dev->pdev, 0));
+	arch_io_free_memtype_wc(start, len);
 	return ret;
 }