ADT7461A and NCT1008 support the undocumented manufacturer and chip ID
registers at 0x3e and 0x3f, and return 0x61 as chip ID. ADM1032 and
ADT7461 do not support those registers but return 0 when reading them.
Use this information to improve the accuracy of the chip detection code.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>