Add AMD IOMMU support into hypervisor

Hi,
The following 2 patches add basic AMD IOMMU support into hypervisor which are adapted to the framework of vt-d/Neo patches. Preliminary tests have been done in both iommu-equipped machines and non-iommu machines, more will be performed later. All patches apply to C/S 15924. To enable AMD IOMMU, please add "enable_amd_iommu" to xen boot parameter.

amd_iommu.patch: h/w detection and initialization, Enable 1:1 mapping for dom0 devices.

misc.patch: Changes to xen code.

Wei