dt-bindings: Use 'additionalProperties' instead of 'unevaluatedProperties'

dt-bindings: Use 'additionalProperties' instead of 'unevaluatedProperties'

In cases where we don't reference another schema, 'additionalProperties'
can be used instead. This is preferred for now as 'unevaluatedProperties'
support isn't implemented yet.

In a few cases, this means adding some missing property definitions of
which most are for SPI bus properties. 'unevaluatedProperties' is not going
to work for the SPI bus properties anyways as they are evaluated from the
parent node, not the SPI child node.

Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20201005183830.486085-3-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>