dt-bindings: display: rockchip,dw-mipi-dsi: Narrow clocks for rockchip,rk3288-mipi-dsi

The binding allows in top-level from one to four clocks and each variant
narrows the choice, but rockchip,rk3288-mipi-dsi missed the minItems.

Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250820-dt-bindings-display-v2-3-91e2ccba3d4e@linaro.org


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>