rtc: sc27xx: Always read normal alarm

The RTC core only reads the alarm from the hardware at boot time, to know
whether an alarm was already set before booting. It keeps track of all the
alarms after that so there is no need to ever read the auxiliary alarm.

Commit 3822d1bb ("rtc: sc27xx: Always read normal alarm when
registering RTC device") already effectively removed the capability to read
the auxiliary alarm as .read_alarm is always called with rtc->registered set
to false.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Chunyan Zhang <zhang.lyra@gmail.com>
Link: https://lore.kernel.org/r/20201117212201.1288608-1-alexandre.belloni@bootlin.com