dt-bindings: display: rockchip,vop: Drop assigned-clocks

assigned-clock properties are implicitly allowed in any node with
'clocks' and don't have to be specified. The max here also appears to be
wrong as there's a case with 4 entries.

Signed-off-by: "Rob Herring (Arm)" <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20250404214030.401629-1-robh@kernel.org