agp: Support 64-bit APBASE

Per the AGP 3.0 spec, APBASE is a standard PCI BAR and may be either 32
bits or 64 bits wide.  Many drivers read APBASE directly, but they only
handled 32-bit BARs.

The PCI core reads APBASE at enumeration-time.  Use pci_bus_address()
instead of reading it again in the driver.  This works correctly for both
32-bit and 64-bit BARs.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/char/agp/agp.h

@@ -239,6 +239,7 @@ long compat_agp_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
 
 /* Chipset independent registers (from AGP Spec) */
 #define AGP_APBASE	0x10
+#define AGP_APERTURE_BAR	0
 
 #define AGPSTAT		0x4
 #define AGPCMD		0x8