fdt: Fix fdt_pci_dma_ranges handling of 64-bit ranges

If the size of a region equal to 4G it can't be represnted in a 32-bit
BAR so we should have marked that case as MEM64.

Additionally bump the number of inbound windows up to 4 to handle the
fact that Freescale PPCs that have an implicit window for CCSRBAR.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>