hwmon: (asus-ec-sensors) Add support for fan cpu opt on AMD 600 motherboards

hwmon: (asus-ec-sensors) Add support for fan cpu opt on AMD 600 motherboards

According to the LibreHardwareMonitor project, LibreHardwareMonitorLib/
Hardware/Motherboard/Lpc/EC/EmbeddedController.cs file, fan cpu opt
is supported by the AMD600 EC. Registers are described as follows.

BoardFamily.Amd600, new Dictionary<ECSensor, EmbeddedControllerSource>
{
{ ECSensor.FanCPUOpt,  new EmbeddedControllerSource
("CPU Optional Fan", SensorType.Fan, 0x00b0, 2) },
}

Add FanCPUOpt support for AMD600.

Signed-off-by: Li XingYang <yanhuoguifan@gmail.com>
[groeck: Massaged subject and description]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>