On the 83xx platform to ensure the PCI inbound memory is handled properly we
have to turn on coherency for all pages in the MMU.  Otherwise we see
corruption if inbound "prefetching/streaming" is enabled on the PCI controller.
Signed-off-by: Randy Vinson <rvinson@mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>