MAINTAINERS: Update mailing list and web page for hwmon subsystem

commit 968ce1b1 upstream.

The old web page for the hwmon subsystem is no longer operational,
and the mailing list has become unreliable. Move both to kernel.org.
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
[bwh: Backported to 3.16: the set of hwmon drivers is different, so do a
 search-and-replace for the same addresses]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>