powerpc/44x: Use for_each_of_range() iterator

Simplify the ppc44x PCI dma-ranges parsing to use the
for_each_of_range() iterator.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241106212640.341677-1-robh@kernel.org