watchdog: w83627hf_wdt: Add quirk for Inves system

On some systems, the NCT6791D comes with a companion chip and the
watchdog function is in this companion chip. We must use a different
unlocking sequence to access the companion chip.

Use DMI strings to identify such system and adjust the unlocking
sequence automatically.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>