ARM: OMAP1: PM fixes for OMAP1

This patch does the following:

- Fixes the omap_pm_idle() code so that we enter WFI mode in idle.
- /sys/power/sleep_while_idle is created only when 32k timer is used

Signed-off-by: Vivek Kutal <vivek.kutal@celunite.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>