ARM: omap-device: add missed callback for suspend-to-disk

Add missed callback needed for supporting suspend-to-disk (hibernation) mode.

Signed-off-by: Grygorii Strashko <Grygorii.Strashko@linaro.org>
Acked-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>