vgaarb: Stop complaining about absent devices

Some setups do not register a default VGA device, in which case the VGA
arbiter will still complain about the (non-existent) PCI device being a
non-VGA device.

Fix this by making the error message conditional on a default VGA device
having been set up. Note that the easy route of erroring out early isn't
going to work because otherwise priv->target won't be properly updated.
Signed-off-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/vga/vgaarb.c

@@ -1091,8 +1091,11 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
 		vgadev = vgadev_find(pdev);
 		pr_debug("vgaarb: vgadev %p\n", vgadev);
 		if (vgadev == NULL) {
-			pr_err("vgaarb: this pci device is not a vga device\n");
-			pci_dev_put(pdev);
+			if (pdev) {
+				pr_err("vgaarb: this pci device is not a vga device\n");
+				pci_dev_put(pdev);
+			}
+
 			ret_val = -ENODEV;
 			goto done;
 		}