drivers/rtc: broken link fix

In drivers/rtc/rtc-rx8025.c is a broken link that is supposed to
lead to a form allowing users to subscribe to the lm-sensors mailing list.

The link <http://lists.lm-sensors.org/mailman/listinfo/lmsensors

> leads
to a page with a 404 error. I believe the link should be replaced
with <lm-sensors@lm-sensors.org>.

Signed-off-by: Leslie Lau <laulinxk@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>