There's a few custom bus bindings (e.g. fsl,qoriq-mc) which use a
3 cell format with custom flags in the high cell. We can match these
buses as a fallback if we didn't match on PCI bus which is the only
standard bus binding with 3 address cells.

Link: https://lore.kernel.org/r/20230328-dt-address-helpers-v1-3-e2456c3e77ab@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>