dt-bindings: mfd: rohm,bd71837-pmic: Add common properties

Add common properties appearing in DTSes (clock-names,
clock-output-names) with the common values (actually used in DTSes) to
fix dtbs_check warnings like:

  arch/arm64/boot/dts/freescale/imx8mq-librem5-r2.dt.yaml:
    pmic@4b: 'clock-names', 'clock-output-names', do not match any of the regexes: 'pinctrl-[0-9]+'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-By: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/rohm,bd71837-pmic.yaml

@@ -32,9 +32,15 @@ properties:
   clocks:
     maxItems: 1
 
+  clock-names:
+    const: osc
+
   "#clock-cells":
     const: 0
 
+  clock-output-names:
+    const: pmic_clk
+
 # The BD718x7 supports 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 and external