of: unittest: Add bus address range parsing tests

While there are tests for "dma-ranges" helpers, "ranges" is missing any
tests. It's the same underlying code, but for completeness add a test
for "ranges" parsing iterators. This is in preparation to add some
additional "ranges" helpers.

Link: https://lore.kernel.org/r/20230328-dt-address-helpers-v1-1-e2456c3e77ab@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>