Now that we understand (and have fixed) the problem with using low power mode
in the idle loop, lets enable it.  It should save a fair amount of power.

(The problem was that our exceptions were inheriting the low power mode and so
were executing at a fraction of the normal cpu issue rate.  We fixed it by
always bumping our priority to medium at the start of every exception).
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>