hwmon: (vt8231) Add individual alarm files

The new libsensors needs these individual alarm files.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
CC: Roger Lucas <vt8231@hiddenengine.co.uk>
Acked-by: Juerg Haefliger <juergh at gmail.com>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>