ARM: PRM: AM437x: Enable IO wakeup feature

Enable IO wakeup feature. This enables am437x pads to generate daisy
chained wake ups(eventually generates aprcm Interrupt) especially
when in low power modes.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>