x86/amd-iommu: Use dev->arch->iommu to store iommu related information

This patch changes IOMMU code to use dev->archdata->iommu to
store information about the alias device and the domain the
device is attached to.
This allows the driver to get rid of the amd_iommu_pd_table
in the future.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>