hwmon: (nct7904) Add extra sysfs support for fan, voltage and temperature.

NCT-7904D also supports reading of channel limitation registers as well
as SMI status registers for fan, voltage and temperature monitoring.
It also supports reading the temperature sensor type (thermal diode,
thermistor, AMD SB-TSI or Intel PECI).

Add the following sysfs nodes:

-fan[1-*]_min
-fan[1-*]_alarm
-in[1-*]_min
-in[1-*]_max
-in[1-*]_alarm
-temp[1-*]_max
-temp[1-*]_max_hyst
-temp[1-*]_emergency
-temp[1-*]_emergency_hyst
-temp[1-*]_alarm
-temp[1-*]_type
Signed-off-by: Amy Shih <amy.shih@advantech.com.tw>
Link: https://lore.kernel.org/r/20190807013842.24451-1-Amy.Shih@advantech.com.tw
[groeck: Clarified description]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>