This adds support for specifying the address space used by a bridge child; this will either be the bridged SoC address space, or the host address space required by children that map non SoC-address ranges from the PCI BAR.
This is necessary to support SROM/OTP child devices that live directly beneath the bhndb device and require access to host resources, instead of the standard behavior of delegating access to the bridged SoC address space.