rtc: ab-eoz9: don't fail temperature reads on undervoltage notification

[ Upstream commit e0779a0dcf41a6452ac0a169cd96863feb5787c7 ]

The undervoltage flags reported by the RTC are useful to know if the
time and date are reliable after a reboot. Although the threshold VLOW1
indicates that the thermometer has been shutdown and time compensation
is off, it doesn't mean that the temperature readout is currently
impossible.

As the system is running, the RTC voltage is now fully established and
we can read the temperature.

Fixes: 67075b63 ("rtc: add AB-RTCMC-32.768kHz-EOZ9 RTC support")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://lore.kernel.org/r/20241122101031.68916-3-maxime.chevallier@bootlin.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>