rtc: mv: remove mv_rtc_alarm_ops

Move the alarm callbacks in mv_rtc_ops and clear RTC_FEATURE_ALARM to
signal that alarms are not available instead of having a supplementary
struct rtc_class_ops.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210110231752.1418816-6-alexandre.belloni@bootlin.com