hwmon: (lm63) Expose automatic fan speed control lookup table

The LM63 and compatible devices have a lookup table to control the fan
speed automatically. Expose it in sysfs. Values are cached for 5
seconds, independently of the other register values to avoid slowing
down "sensors". We might make the table values writable in the future.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>

Documentation/hwmon/lm63

@@ -66,7 +66,8 @@ supported either.
 
 The lm63 driver will not update its values more frequently than configured with
 the update_interval sysfs attribute; reading them more often will do no harm,
-but will return 'old' values.
+but will return 'old' values. Values in the automatic fan control lookup table
+(attributes pwm1_auto_*) have their own independent lifetime of 5 seconds.
 
 The LM64 is effectively an LM63 with GPIO lines. The driver does not
 support these GPIO lines at present.