dt-bindings: rtc: Move rv3028 from trivial-rtc.yaml into own schema file

Move RV3028 RTC bindings from trivial-rtc.yaml into microcrystal,rv3032.yaml.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230111163404.3526248-2-w.egorov@phytec.de


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