dt-bindings: Move sophgo,cv1800b-rtc to rtc directory

dt-bindings: Move sophgo,cv1800b-rtc to rtc directory

The $id path for the sophgo,cv1800b-rtc binding was missing part of the
path 'soc'. However, the correct place for RTC bindings (even if it's
also a "syscon") is the rtc directory, so move the binding there while
fixing the $id value.

Fixes: 76517429dbfd ("dt-bindings: soc: sophgo: add RTC support for Sophgo CV1800 series")
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250608224252.3902421-1-robh@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>