[PATCH] rcutorture: catchup doc fixes for idle-hz tests

This just catches the RCU torture documentation up with the recent fixes
that test RCU for architectures that turn of the scheduling-clock interrupt
for idle CPUs and the addition of a SUCCESS/FAILURE indication, fixing up
an obsolete comment as well.

Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>