hwmon: (occ) Move common code to a separate module

Instead of duplicating the common code into the 2 (binary) drivers,
move the common code to a separate module. This is cleaner.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Eddie James <eajames@linux.ibm.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Tested-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>