A few small fixes:

- Check for the model property before using it. Also check for the
  correct property name for nighthawk.
- Check for the existence of freeze-time-base before using it to
  synchronize timebases instead of making it conditional on !LPAR
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>