powerpc/86xx: Update 8641hpcn dts file to match latest u-boot

The newest revision of uboot reworks the memory map for this
board to look more like the 85xx boards.  Also, some regions
which were far larger than the actual hardware have been scaled
back to match the board, and the imaginary second flash bank has
been removed. Rapidio and PCI are mutually exclusive in the hardware,
and they now are occupying the same space in the address map.
The Rapidio node is commented out of the .dts since PCI is the
common use case.

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