dt-bindings: phy: ti,phy-am654-serdes: drop assigned-clocks type

dt-bindings: phy: ti,phy-am654-serdes: drop assigned-clocks type

The meta schema from DT schema already defines assigned-clocks, so there
is no need for device schema to mention it at all.  The specific
parenting of the first input and output clock is apparently important,
thus keep them as required, but without defining type.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230404190115.546973-3-krzysztof.kozlowski@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>