dt-bindings: rtc: Move isil,isl12022 from trivial-rtc.yaml into own schema file

Move the isil,isl12022 RTC bindings from trivial-rtc.yaml into its own
intersil,isl12022.yaml file, in preparation for adding more bindings.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20230615105826.411953-3-linux@rasmusvillemoes.dk


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