hwmon: (max6639) fix inverted polarity

According to MAX6639 documentation:

D1: PWM Output Polarity. PWM output is low at
100% duty cycle when this bit is set to zero. PWM
output is high at 100% duty cycle when this bit is set
to 1.

Up to commit 0f33272b60ed ("hwmon: (max6639) : Update hwmon init using
info structure"), the polarity was set to high (0x2) when no platform
data was set. After the patch, the polarity register wasn't set anymore
if no platform data was specified. Nowadays, since commit 7506ebcd662b
("hwmon: (max6639) : Configure based on DT property"), it is always set
to low which doesn't match with the comment above and change the
behavior compared to versions prior 0f33272b60ed.

Fixes: 0f33272b60ed ("hwmon: (max6639) : Update hwmon init using info structure")
Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Link: https://lore.kernel.org/r/20260304212039.570274-1-olivier@sobrie.be
Signed-off-by: Guenter Roeck <linux@roeck-us.net>