Jetson Nano A02 fix - Сooler was not spin when overheated

[d3dx13]

I came across an interesting feature of this truly cool and compact project.

In short, I needed to invert the feed value in /sys/devices/pwm-fan/target_pwm. 255 was to turn the cooler off and 0 was to turn it to maximum.

I wanted to play around with the desired processor temperatures and set the maximum temperature below that of my room to 35 degrees. To my deepest surprise, the cooler stopped spinning and wouldn't start, even when the hot even without overclocking the jetson warmed up to 45 degrees.
At first I thought that the value fed as pwm was out of range of 0 and 255, but your code already solved this problem perfectly. Then I tried setting the maximum desired temperatures much higher than adequate, and the cooler on the Jetson Nano started to take off. Then I realized that the control is inverted somehow, so I tried "flipping" the pwm control byte, and now it works adequately.

I don't know if it's only a difference between the Jetson Nano A2 and B1 boards, but it's definitely not OS related, as I've tried the latest versions of JetPack and the commuity version on Xubuntu. If you have a chance to check on the B1, that would be fine, for that I left a simple debug of the pwm feed. Although, you can also check it through the console by feeding 0 and 255 to /sys/devices/pwm-fan/target_pwm and see when the cooler is spinning.

If it is a bug, I don't want to leave it in such a cool project, and I want to make my own contribution to its development, however small.

[Pyrestone]

@d3dx13 please adapt the comments. I would like to merge this, but would like to have it cleaned up first.
Especially the default behaviour should not be an inverted pin, as this will likely be a rather rare case.