xen/arm: Handle translated addresses for hardware domains in GICv2

xen/arm: Handle translated addresses for hardware domains in GICv2

Translated addresses (in d->arch.vgic.{c,d}base) are bus addresses
which are not always correct in the context of a subnode in the DTB
exposed to domain 0 since they would then be subject to retranslation.

Copy the original addresses from DT directly to get the original
untranslated reg property which will give same d->arch.vgic.{c,d}base
values once translated again by the guest.

Signed-off-by: Frediano Ziglio <frediano.ziglio@huawei.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
[ ijc -- attempt to clarify the commit message ]