of: unittest: Add test for of_dma_get_max_cpu_address()

Introduce a test for of_dma_get_max_cup_address(), it uses the same DT
data as the rest of dma-ranges unit tests.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201119175400.9995-5-nsaenzjulienne@suse.de
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>