rtc: ds1685: switch to RTC_FEATURE_UPDATE_INTERRUPT

Stop using uie_unsupported and clear RTC_FEATURE_UPDATE_INTERRUPT instead.
There is currently a missing information as to why this is not supported on
ioc3.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220309162301.61679-1-alexandre.belloni@bootlin.com