Implement handling properties in subnodes and adding child devices to the
system. Child devices will not be added if configuration fails.

Since the driver now does more than suspend-resume support, dependency on
CONFIG_PM is removed.
Signed-off-by: NPavel Fedin <p.fedin@samsung.com>
Reviewed-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NPankaj Dubey <pankaj.dubey@samsung.com>
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>