intel-iommu: Handle PCI domains appropriately.

We were comparing {bus,devfn} and assuming that a match meant it was the
same device. It doesn't -- the same {bus,devfn} can exist in
multiple PCI domains. Include domain number in device identification
(and call it 'segment' in most places, because there's already a lot of
references to 'domain' which means something else, and this code is
infected with ACPI thinking already).

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

include/linux/dmar.h

@@ -34,6 +34,7 @@ struct dmar_drhd_unit {
 	u64	reg_base_addr;		/* register base address*/
 	struct	pci_dev **devices; 	/* target device array	*/
 	int	devices_cnt;		/* target device count	*/
+	u16	segment;		/* PCI domain		*/
 	u8	ignored:1; 		/* ignore drhd		*/
 	u8	include_all:1;
 	struct intel_iommu *iommu;