dt-bindings: leds: lp55xx: rework to match multi-led

The binding allows two type of LEDs - single and multi-color.  They
differ with properties, so fix the bindings to accept both cases.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221127204058.57111-5-krzysztof.kozlowski@linaro.org


Signed-off-by: Rob Herring <robh@kernel.org>