dt-bindings: white-space cleanups

Remove trailing white-spaces and trailing blank lines (yamllint with
default options does not like them).

Suggested-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220402192819.154691-1-krzysztof.kozlowski@linaro.org