of/address: Fix variable name in comment of of_iomap

The first variable name of of_iomap is np while previous
comment write device here.

Signed-off-by: Wenchao Hao <haowenchao22@gmail.com>
Link: https://lore.kernel.org/r/20200701162444.9494-1-haowenchao22@gmail.com


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