spi: dt-bindings: Add bindings for RZ/V2M CSI

Add dt-bindings for the CSI IP found inside the RZ/V2M SoC.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/Message-Id

: <20230622113341.657842-2-fabrizio.castro.jz@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>