of: unittest: Use bigger address cells to catch parser regressions

Getting address and size cells for dma-ranges/ranges parsing is tricky
and shouldn't rely on the node's count_cells() method. The function
starts looking for cells on the parent node, as its supposed to work
with device nodes, which doesn't work when input with bus nodes, as
generally done when parsing ranges.

Add test to catch regressions on that specific quirk as developers will
be tempted to edit it out in favor of the default method.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/9200970a917a9cabdc5b17483b5a8725111eb9d0.camel@suse.de
Signed-off-by: Rob Herring <robh@kernel.org>