[AGPGART] Fix pci_register_driver checking in amd64-agp

pci_register_driver() never returns a positive number.
Signed-off-by: NDave Jones <davej@redhat.com>

drivers/char/agp/amd64-agp.c

@@ -761,7 +761,7 @@ int __init agp_amd64_init(void)
 
 	if (agp_off)
 		return -EINVAL;
-	if (pci_register_driver(&agp_amd64_pci_driver) > 0) {
+	if (pci_register_driver(&agp_amd64_pci_driver) < 0) {
 		struct pci_dev *dev;
 		if (!agp_try_unsupported && !agp_try_unsupported_boot) {
 			printk(KERN_INFO PFX "No supported AGP bridge found.\n");