README: Add comment about ASUS desktop boards

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
nct6775: Monitor additional temperature registers

The number of SMIOVT registers on NCT6779 and NCT6791 is limited to 2.
As result, the driver may not report some of the temperatures used for fan
control. Fortunately, the chip has registers to monitor those temperatures.
Add them to the list of temperatures to report.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>