powerpc: make dma_window_* in pci_controller struct avail on 32b

Also, convert them to resource_size_t (which is unsigned long
on 64-bit, so it's not a change there).

We will be using these on fsl 32b to indicate the start and size
address of memory that the pci controller can actually reach - this
is needed to determine if an address requires bounce buffering.  For
now, initialize them to a standard value; in the near future, the
value will be calculated based on how the inbound windows are
programmed.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Acked-by: Ben Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>