When trying to use ad_cpu_interconnect to connect to a AXI interface that
is a outer port of a hierarchy this will fail at the moment as it kind find
the matching clock and reset signals.
Add support for traversing into the hierarchy and find the final target AXI
port inside the hierarchy. Then find the matching clock and reset and
traverse them back the corresponding hierarchy outer ports.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>