media: dt-bindings: rcar_vin: Document RZ/G1 per-board settings

The R-Car Gen2 per-board settings apply to RZ/G1, too.

Fixes: 1d14a5ea ("media: dt-bindings: media: rcar_vin: add device tree support for r8a774[35]")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>