rtc: rx8010: drop a struct rtc_class_ops

Merge both struct rtc_class_ops in a single one and use RTC_FEATURE_ALARM
to signal to the core whether alarms are available.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210110231752.1418816-10-alexandre.belloni@bootlin.com