hwmon: (nct6775) Enable both AUXTIN and VIN3 on NCT6776

Per datasheet, VIN3 and AUXTIN share the same external pin. However, there
is no clean way to detect this condition. Furthermore, both are reported
by the BIOS on Supermicro C7H61. It may thus be possible that chip revisions
exist where both attributes are supported at the same time.
Better play safe and report both.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>