media: dt-bindings: media: renesas,vsp1: Document RZ/V2L VSPD bindings

Document VSPD found in RZ/V2L SoC. The VSPD block is identical to RZ/G2L
SoC and therefore use RZ/G2L fallback to avoid any driver changes.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>