dt-bindings: Remove cases of 'allOf' containing a '$ref'

json-schema versions draft7 and earlier have a weird behavior in that
any keywords combined with a '$ref' are ignored (silently). The correct
form was to put a '$ref' under an 'allOf'. This behavior is now changed
in the 2019-09 json-schema spec and '$ref' can be mixed with other
keywords. The json-schema library doesn't yet support this, but the
tooling now does a fixup for this and either way works.

This has been a constant source of review comments, so let's change this
treewide so everyone copies the simpler syntax.

Scripted with ruamel.yaml with some manual fixups. Some minor whitespace
changes from the script.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-By: Vinod Koul <vkoul@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de> # for I2C
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> #for-iio
Reviewed-by: Stephen Boyd <sboyd@kernel.org> # clock
Signed-off-by: Rob Herring <robh@kernel.org>