drm/qxl: Use pci_is_vga() to identify VGA devices

Use pci_is_vga() to identify VGA devices instead of a private is_vga()
function.

This means qxl will use the VGA arbiter for old PCI_CLASS_NOT_DEFINED_VGA
(0x0001) devices as well as the PCI_CLASS_DISPLAY_VGA (0x0300) devices it
recognized previously.

This probably doesn't make a difference because qxl_pci_driver doesn't
claim PCI_CLASS_NOT_DEFINED_VGA devices by default, so it's mainly a code
simplification.

Link: https://lore.kernel.org/r/20230830111532.444535-6-sui.jingfeng@linux.dev
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>

Author: Sui Jingfeng

drivers/gpu/drm/qxl/qxl_drv.c

@@ -68,11 +68,6 @@ module_param_named(num_heads, qxl_num_crtc, int, 0400);
 static struct drm_driver qxl_driver;
 static struct pci_driver qxl_pci_driver;
 
-static bool is_vga(struct pci_dev *pdev)
-{
-	return pdev->class == PCI_CLASS_DISPLAY_VGA << 8;
-}
-
 static int
 qxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
@@ -100,7 +95,7 @@ qxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (ret)
 		goto disable_pci;
 
-	if (is_vga(pdev) && pdev->revision < 5) {
+	if (pci_is_vga(pdev) && pdev->revision < 5) {
 		ret = vga_get_interruptible(pdev, VGA_RSRC_LEGACY_IO);
 		if (ret) {
 			DRM_ERROR("can't get legacy vga ioports\n");
@@ -131,7 +126,7 @@ qxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 unload:
 	qxl_device_fini(qdev);
 put_vga:
-	if (is_vga(pdev) && pdev->revision < 5)
+	if (pci_is_vga(pdev) && pdev->revision < 5)
 		vga_put(pdev, VGA_RSRC_LEGACY_IO);
 disable_pci:
 	pci_disable_device(pdev);
@@ -159,7 +154,7 @@ qxl_pci_remove(struct pci_dev *pdev)
 
 	drm_dev_unregister(dev);
 	drm_atomic_helper_shutdown(dev);
-	if (is_vga(pdev) && pdev->revision < 5)
+	if (pci_is_vga(pdev) && pdev->revision < 5)
 		vga_put(pdev, VGA_RSRC_LEGACY_IO);
 }