dt-bindings: rtc: pcf2123: convert to YAML

Convert the existing txt binding to the preferred YAML format.

The pcf2123 node may contain SPI settings such as spi-cs-high and
spi-max-frequency, which keeps it from being added to the trivial-rtc
binding with its current definition. Add a reference to
spi-peripheral-props.yaml to account for that.

The "interrupts" property was missing in the binding although it is
already supported. Add the missing property in the new binding.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230907-topic-pcf2123_yaml-v2-1-ea87a8e12190@gmail.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>