Fix fencepost error in x86_64 IOMMU (2.6)

There's a fencepost error in the GART IOMMU handling on x86_64 in the unmap path. When testing to see if the bus address is within the IOMMU window and needs to be unmapped, the start of the first page *beyond* the window also passes the test. This can cause the first doubleword of the next page beyond the gatt table to be smashed to zero, with unpredictable results depending on what that page is used for.

Patch attached for 2.6. 2.4 patch already sent separately.

@@ -521,7 +521,7 @@ void pci_unmap_single(struct pci_dev *hw
 	int npages;
 	int i;
 	if (dma_addr < iommu_bus_base + EMERGENCY_PAGES*PAGE_SIZE || 
-	    dma_addr > iommu_bus_base + iommu_size)
+	    dma_addr >= iommu_bus_base + iommu_size)
 		return;
 	iommu_page = (dma_addr - iommu_bus_base)>>PAGE_SHIFT;	
 	npages = to_pages(dma_addr, size);