MAINTAINERS: Update mailing list and web page for hwmon subsystem

commit 968ce1b1f45a7d76b5471b19bd035dbecc72f32d 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>