dt-bindings: power: supply: bq25890: allow power-supply fields

The BQ25890 schema references common power-supply.yaml, so allow all its
properties to fix warnings like:

  arch/arm64/boot/dts/freescale/imx8mq-librem5-r2.dtb: charger@6a: 'monitored-battery', 'power-supplies', ... do not match any of the regexes: 'pinctrl-[0-9]+'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>