media: dt-bindings: media: rkisp1: complete ov2685 example

With the upcoming conversion of ov2685 to dt-schema let's complete the
example so validation succeeds. At the same time fix the indentation of
the port node in this example.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>