dt-bindings: fsl: imx7ulp-smc1: Add #clock-cells property

dt-bindings: fsl: imx7ulp-smc1: Add #clock-cells property

The SMC1 block on i.MX7ULP is already used as a clock provider in
imx7ulp.dtsi, but the corresponding dt-binding schema does not define
the required '#clock-cells' property. This results in CHECK_DTBS schema
validation errors.

Functionally, SMC1 controls the CPU run mode configuration:
  - 00b: Normal Run (RUN)
  - 10b: Very-Low-Power Run (VLPR)
  - 11b: High-Speed Run (HSRUN)

These run modes determine the effective CPU operating point, and their
programming is tied to the OPP table.

Add the missing `#clock-cells` definition so the dt-binding schema is
consistent with the DTS and validates correctly.

Fixes: 8ba41d6bd9893 ("dt-bindings: fsl: Convert i.MX7ULP PM to json-schema")
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>