of/address: introduce of_address_count() helper

Introduce of_address_count() helper to count the IO resources
instead of open-coding it.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221008115617.3583890-2-yangyingliang@huawei.com


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