[POWERPC] 4xx: Change Kilauea PCIe bus ranges in dts file

Currently we have some limitations in the 4xx PCIe driver and can't
support all possible PCIe busses. But the current limits in the
dts file are quite low (only 16 busses per RC). This patch increases
the number to 64 per RC.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>