dt-bindings: rtc: add schema for NXP S32G2/S32G3 SoCs

dt-bindings: rtc: add schema for NXP S32G2/S32G3 SoCs

RTC tracks clock time during system suspend and it is used as a wakeup
source on S32G2/S32G3 architecture.

RTC from S32G2/S32G3 is not battery-powered and it is not kept alive
during system reset.

Co-developed-by: Bogdan-Gabriel Roman <bogdan-gabriel.roman@nxp.com>
Signed-off-by: Bogdan-Gabriel Roman <bogdan-gabriel.roman@nxp.com>
Co-developed-by: Ghennadi Procopciuc <ghennadi.procopciuc@nxp.com>
Signed-off-by: Ghennadi Procopciuc <ghennadi.procopciuc@nxp.com>
Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250403103346.3064895-2-ciprianmarian.costea@oss.nxp.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>