dt-bindings: Clean-up undocumented compatible strings

Adding checks for undocumented compatible strings reveals a bunch of
warnings in the DT binding examples. Fix the cases which are typos, just
a mismatch between the schema and the example, or aren't documented at all.
In a couple of cases, fixing the compatible revealed some schema errors
which are fixed.

There's a bunch of others remaining after this which have bindings, but
those aren't converted to schema yet.

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux-clk@vger.kernel.org
Cc: dmaengine@vger.kernel.org
Cc: linux-i3c@lists.infradead.org
Cc: linux-iio@vger.kernel.org
Cc: linux-leds@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-serial@vger.kernel.org
Cc: linux-spi@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Acked-by: Sebastian Reichel <sre@kernel.org>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Vinod Koul <vkoul@kernel.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Alain Volmat <alain.volmat@foss.st.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20210316194918.3528417-1-robh@kernel.org