omap: device: improve errors handling

Do not forget to check the 'platform_device_add_data()' error code
in 'omap_device_build_ss()'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Nishanth Menon <nm@ti.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>