nouveau/headers: Make nvk_cl**** turn to nv_cl****

What does this MR do and why?

I have been working on a new gallium driver on the side for nouveau. This MR splits
things up so new drivers can use more of the common functions within NVK. This is based
on the current needs of the gallium driver I have been writing for fun which may change
in the future.

I dont know if I will actually finish my gallium driver as I am just working on it for fun
and I have other projects I need to work on and honestly I like zink better, hence the early
MR for this and its partial RFC status. Perhaps if someone has a better idea like a CUDA
runtime or the like they could use this as a base.

If there are any comments on how this code sharing could be improved I would appreciate it.