hwmon: (it87) Add support for second Super-IO chip

The Super-IO chip can also reside at SIO address 0x4e, and there can be
two Super-IO chips in the system. Add support for it.

Tested-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>