powerpc/ppc/ppc64: Various compile fixes.

This declares powersave_nap in system.h and makes it an int everywhere,
fixes typos for the maple platform, fixes a couple of places where
I missed removing the last two arguments from a message_pass function,
and makes ppc64 consistent with ppc32 in the type of the
pci_bridge.cfg_data field.

Signed-off-by: Paul Mackerras <paulus@samba.org>