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>