[SPARC64]: Fix IO/MEM space sizing for PCI.

In pci_determine_mem_io_space(), do not hard code the region sizes.
Instead, use the values given to us in the ranges property.

Thanks goes to Mikael Petterson for the original Xorg failure
bug repoert, and strace dumps from Mikael and Dmitry Artamonow.

Signed-off-by: David S. Miller <davem@davemloft.net>