hwmon: (dell-smm) Add Latitude 5480 to fan control whitelist

This allows manual PWM control without the BIOS fighting back on Dell
Latitude 5480.

Signed-off-by: Jeffrey Lin <jeffrey@icurse.nl>
Acked-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20200621045246.929649-1-jeffrey@icurse.nl


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