hwmon: (w83627ehf) Fix number of fans for NCT6776F

NCT6776F can select fan input pins for fans 3 to 5 with a secondary set of
chip register bits. Check that second set of bits in addition to the first set
to detect if fans 3..5 are monitored.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: stable@vger.kernel.org # 3.0+
Acked-by: Jean Delvare <khali@linux-fr.org>