[POWERPC] Hide resources on Axon PCIE root complex nodes

The PCI bridge representing the PCIE root complex on Axon, contains
device BARs for a memory range and ROM that define inbound accesses.
This confuses the kernel resource management code -- the resources
need to be hidden when Axon is a host bridge.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>