Support the variant of the interrupt-map property where the parent bus has
the #address-cells property set. For this we need to read more data before
the parent interrupt description.

this is only enabled on arm64 for now as it's not quite compliant with the
ePAPR spec. We should use a default of 2 where the #address-cells property
is missing, however this will need further testing across architectures.

Obtained from: ABT Systems Ltd
Sponsored by: SoftIron Inc
Differential Revision: https://reviews.freebsd.org/D4518