dt-bindings: rtc: abx80x: convert to yaml

Convert the abracon abx80x rtc text bindings to dt-schema format.

In addition to the text description reference generic interrupts
properties and add an example.

Signed-off-by: Josua Mayer <josua@solid-run.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240219-rtc-abracon-convert-bindings-v7-1-aca4fc3b8cec@solid-run.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>