powerpc/pci: Update bridge windows on PCI plug

On the PCI plugging event, PCI slot's subordinate devices are
scanned and their (IO and MMIO) resources are assigned. Platform
dependent resources (PE#, IO/MMIO/DMA windows) are allocated or
created on updating windows of the slot's upstream bridge.

This updates the windows of the hot plugged slot's upstream bridge
in pcibios_finish_adding_to_bus() so that the platform resources
(PE#, IO/MMIO/DMA segments) are allocated or created accordingly.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>