x86_64: off-by-two error in aperture.c

I'm using a custom BIOS to configure the northbridge GART at address
0x80000000, size 2G.  Linux complains:

"Aperture from northbridge cpu 0 beyond 4GB. Ignoring."

I think there's an off-by-two error in arch/x86_64/kernel/aperture.c:

AK: use correct types for i386

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index 373ef66..ae091cd 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -476,7 +476,7 @@
 	aper_base <<= 25;
 
 	aper_size = (32 * 1024 * 1024) << aper_order; 
-	if (aper_base + aper_size >= 0xffffffff || !aper_size)
+       if (aper_base + aper_size > 0x100000000UL || !aper_size)
 		aper_base = 0;
 
 	*size = aper_size;