AMD/IOMMU: allocate one device table per PCI segment

AMD/IOMMU: allocate one device table per PCI segment

Having a single device table for all segments can't possibly be right.
(Even worse, the symbol wasn't static despite being used in just one
source file.) Attach the device tables to their respective IVRS mapping
ones.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Juergen Gross <jgross@suse.com>