rtc: ds1685: do not sleep in the power-off handler

Power-off handlers run from an atomic notifier chain and must not
sleep. Use mdelay() for the delay before setting PAB.

Fixes: aaaf5fbf56f1 ("rtc: add driver for DS1685 family of real time clocks")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/sashiko-outbox-169477@kernel.org/
Signed-off-by: Imre Kaloz <kaloz@kernel.org>
Acked-by: Joshua Kinard <linux@kumba.dev>
Link: https://patch.msgid.link/20261013120208.11268-3-kaloz@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>