dt-bindings: iio: Correct indentation and style in DTS example

dt-bindings: iio: Correct indentation and style in DTS example

DTS example in the bindings should be indented with 2- or 4-spaces and
aligned with opening '- |', so correct any differences like 3-spaces or
mixtures 2- and 4-spaces in one binding.

No functional changes here, but saves some comments during reviews of
new patches built on existing code.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250324125313.82226-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>