spi: dt-bindings: Fix unevaluatedProperties warnings in examples

spi: dt-bindings: Fix unevaluatedProperties warnings in examples

The 'unevaluatedProperties' schema checks is not fully working and doesn't
catch some cases where there's a $ref to another schema. A fix is pending,
but results in new warnings in examples.

'spi-max-frequency' is supposed to be a per SPI peripheral device property,
not a SPI controller property, so drop it.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220526014141.2872567-1-robh@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>