As far as I'm aware there is no standardized driver available in QNX. We have ourselves evaluated this scenario some 
years back, and found that the effort is quite considerable (at that time) and the support from TI was not overwhelming 
- very little information on how theses PRUs work, what you need to do, examples and so on.

We then abandoned this approach for a completely different design.

Knowing that there is some driver available in Linux, maybe you could use that as a starting point to implement a 
resource manager that handles the basic tasks - download a firmware image, start it, and provide a mechanism to exchange
 data.

Regards,
Al