Document the new optional properties related to DDR Backup Mode and
toggle/momentary power switches.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NRob Herring <robh@kernel.org>
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NMark Brown <broonie@kernel.org>