rtc: da9063: switch to RTC_FEATURE_UPDATE_INTERRUPT

Stop using uie_unsupported and clear RTC_FEATURE_UPDATE_INTERRUPT instead.
Also, let the core know that the alarm will truncate seconds as it only has
a minute resolution.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Link: https://lore.kernel.org/r/20211109234750.107115-1-alexandre.belloni@bootlin.com