dt-bindings: leds: fix indentation in examples

The examples were mixing 4-space with 2- and 3-space indentations, so
correct them to use 4-space one.  No functional change.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220607075247.58048-2-krzysztof.kozlowski@linaro.org