powerpc: fix pci window initialization to work with > 4GB DRAM

The existing code has a few errors that need to be fixed in
order to support large RAM sizes.  Fix those, and add a
comment to make it clearer.

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
1 file changed