dt-bindings: power: Add Actions Semi S900 SPS

Define power domains for Actions Semi S900 SoC Smart Power System (SPS).

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>