dt-bindings: media: Add missing clock domain description

make dtbs_check:

    arch/arm/boot/dts/r7s72100-genmai.dt.yaml: camera@e8210000: 'clocks', 'power-domains' do not match any of the regexes: 'pinctrl-[0-9]+'

Fix this by documenting the missing properties.
Update the example to match reality.

Fixes: 58361eaa ("dt-bindings: media: renesas,ceu: Convert to yaml")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Rob Herring <robh@kernel.org>