intel-iommu: add Second Level Page Table walking functions

Add some helper functions for SLPT walk. Check if the mapping is
1 to 1.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
q35: add IOMMU address space support

Add basic framework for IOMMU translation. q35 uses pci_setup_iommu() to
register a AddressSpace for IOMMU. Right now q35 uses one AddressSpace for
all buses/devices, this should be fixed later.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
intel-iommu: some trivial fixups

Use PRIx64 for printing uint64_t. Some small fixups.

Signed-off-by: Le Tan <tamlokveer@gmail.com>