hwmon: (w83627hf) Enable VBAT monitoring

If VBAT monitoring is disabled, enable it. Bug reported on the
lm-sensors trac system:
http://lm-sensors.org/ticket/2282
This is the exact same patch that was applied to the w83627ehf driver
6 months ago.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>