hwmon: (asus-ec-sensors) read sensors as signed ints

hwmon: (asus-ec-sensors) read sensors as signed ints

Temperature sensor readings are signed, which is hinted by their blank
value (oxd8, 216 as unsigned and -40 as signed). T_Sensor, Crosshair
VIII Hero, and a freezer were used to confirm that.

Here we read fan sensors as signed too, because with their typical
values and 2-byte width, I can't tell a difference between signed and
unsigned, as I don't have a high speed chipset fan.

Signed-off-by: Eugene Shalygin <eugene.shalygin@gmail.com>
Link: https://lore.kernel.org/r/20220204163045.576903-1-eugene.shalygin@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>