This is against my last.

While the old code most definitely did /something/ to the register for
setting the fan div, the 'what' is a more interesting question.

To be honest I could not figure out what it was trying to do, because
the way it was inserting values disagreed with not only the data sheet,
but how it parsed the very same register.

This corrects the issue, and allows one to properly control the divisor
on all 3 fans, including the (much more limited) 3rd fan.