x86: move warning message of polling idle and HT enabled

The warning message at idle_setup() is never shown because
smp_num_sibling hasn't been updated at this point yet.

Move this polling idle and HT enabled warning to select_idle_routine().
I also implement this warning on 64-bit kernel.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>