rtc: m41t80: reduce verbosity

The driver currently uses dev_err for messages that have a very low probability
of being read by the user as the error will probably never happen and the
systems with the RTC probably don't have any user able to read the message.

Moreover, the only user action after getting this message is the restart the
action so drop the level to dev_dbg.

Link: https://lore.kernel.org/r/20250525222153.1472917-1-alexandre.belloni@bootlin.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>