[PATCH] ppc64: iSeries idle fixups

- remove min/max yield time, we dont use the values anywhere
- separate shared and dedicated idle loops
- check need_resched again with irqs off to avoid sleeping with pending work
- continually set runlatch off in idle loop, this means we dont need to
  turn the runlatch off on exception exit and suffer that associated
  cost for all exceptions. (A future patch will turn the runlatch on at
  exception entry)

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>