The current code will cause the creation of a 4GB window
starting at 0 if we have more than 4GB of RAM installed,
which overlaps with PCI_MEM space and causes pci_bus_to_phys()
to return erroneous information. Limit the size to 4GB - 1;
which causes the code to create one 2GB and one 1GB window
instead.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Andy Fleming <afleming@freescale.com>