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>