dt-bindings: phy: cadence-sierra: drop assigned-clocks

dt-bindings: phy: cadence-sierra: drop assigned-clocks

The meta schema from DT schema already defines assigned-clocks, so there
is no need for device schema to mention it at all.  There are also no
benefits of having it here and a board could actually need more of clock
assignments than the schema allows.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230404190115.546973-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>