dt-bindings: mfd: rohm,bd71847-pmic: Correct clock properties requirements

The input clock and number of clock provider cells are not required for
the PMIC to operate.  They are needed only for the optional bd718x7
clock driver.

Add also clock-output-names as driver takes use of it.

This fixes dtbs_check warnings like:

    arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dt.yaml: pmic@4b: 'clocks' is a required property
    arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dt.yaml: pmic@4b: '#clock-cells' is a required property
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/mfd/rohm,bd71847-pmic.yaml

@@ -38,6 +38,9 @@ properties:
   "#clock-cells":
     const: 0
 
+  clock-output-names:
+    maxItems: 1
+
 # The BD71847 abd BD71850 support two different HW states as reset target
 # states. States are called as SNVS and READY. At READY state all the PMIC
 # power outputs go down and OTP is reload. At the SNVS state all other logic
@@ -116,12 +119,14 @@ required:
   - compatible
   - reg
   - interrupts
-  - clocks
-  - "#clock-cells"
   - regulators
 
 additionalProperties: false
 
+dependencies:
+  '#clock-cells': [clocks]
+  clocks: ['#clock-cells']
+
 examples:
   - |
     #include <dt-bindings/interrupt-controller/irq.h>