of: Allows to use the PCI translator without the PCI core

Translating an address from a PCI node of the device-tree into a CPU
physical address doesn't require the core PCI support. Those
translations are just related to the device tree itself.

The use case to translate an address from a PCI node without actually
using the PCI core support is when one needs to access the PCI
controller without accessing any PCI devices.

Marvell SoCs, such as Kirkwood, Dove or Armada XP for instance, come
with an IP of a PCI controller. In the registers of this controller
are stored the ID and the revision of a SoC. With this patch it will
be possible to read the SoC ID of a board without any PCI device and
then without the PCI core support.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Reviewed-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>