iommu/amd: Manage iommu_group for ACPI HID devices

This patch creates a new function for finding or creating an IOMMU
group for acpihid(ACPI Hardware ID) device.

The acpihid devices with the same devid will be put into same group and
there will have the same domain id and share the same page table.

Signed-off-by: Wan Zongshun <Vincent.Wan@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>