OMAP3: wdtimer: Fix CORE idle transition

The HW superwised smart idle for wdtimer in OMAP3 prevents
CORE power domain idle transitions. Disable it by swithing
to SW supervised transitions.

This could be a hardware bug in the OMAP3 wdtimer2 block.

Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@nokia.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>