rtc: efi: switch to RTC_FEATURE_UPDATE_INTERRUPT

Stop using uie_unsupported and clear RTC_FEATURE_UPDATE_INTERRUPT instead.
Also the driver doesn't supports UIE because it doesn't handle interrupts
so set RTC_FEATURE_ALARM_WAKEUP_ONLY,.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220309162301.61679-24-alexandre.belloni@bootlin.com