dt-bindings: Fix dtc warnings in examples

Fix all the warnings in the DT binding schema examples when built with
'W=1'. This is in preparation to make that the default for examples.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Vinod Koul <vkoul@kernel.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>