iommu/amd: Modify ivhd_header structure to support type 11h and 40h

This patch modifies the existing struct ivhd_header,
which currently only support IVHD type 0x10, to add
new fields from IVHD type 11h and 40h.

It also modifies the pointer calculation to allow
support for IVHD type 11h and 40h

Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>