media: dt-bindings: dongwoon,dw9714: convert to dtschema

Convert Dongwoon Anatech DW9714 camera voice coil lens driver to DT
schema and extend the bindings with vcc-supply (already used by driver)
and powerdown-gpios (based on datasheet, not used by the driver).

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>