[DeviceDriver][RTC] Remove RT_DEVICE_CTRL_RTC_GET_TIME_US and RT_DEVICE_CTRL_RTC_SET_TIME_US. Add RT_DEVICE_CTRL_RTC_GET_TIMEVAL and RT_DEVICE_CTRL_RTC_SET_TIMEVAL. The RT_DEVICE_CTRL_RTC_GET_TIMEVAL cmd can get second time and microsecond time.