AMD/IOMMU: check / convert IVMD ranges for being / to be reserved

AMD/IOMMU: check / convert IVMD ranges for being / to be reserved

While the specification doesn't say so, just like for VT-d's RMRRs no
good can come from these ranges being e.g. conventional RAM or entirely
unmarked and hence usable for placing e.g. PCI device BARs. Check
whether they are, and put in some limited effort to convert to reserved.
(More advanced logic can be added if actual problems are found with this
simplistic variant.)

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul@xen.org>