The IORT table's ID mapping uses a 256-ID offset per PCI segment to
ensure unique device IDs across all segments. This partitioning scheme
(output_base = 256 * segment_id) must match the device ID encoding used
in KVM MSI routing configuration [1].
This mapping assumes one bus per PCI segment, and supports up to 256 PCI
segments in the system.
[1] c9374d87ac
Signed-off-by: Bo Chen <bchen@crusoe.ai>