Set preempt_count of idle_thread to zero before switching off cpu.  Otherwise
the preempt_count will be wrong if the cpu is switched on again since the
thread will be reused.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>