rtc: ds1685: Update Joshua Kinard's email address.

I am switching my address to a personal domain, so need to update the
driver's files and the entry in MAINTAINERS.

Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Link: https://lore.kernel.org/r/20250721170051.32407-1-kumba@gentoo.org


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