agx(v): add queue priority

I decided to implement this in agxv first since agxv does not rely on an agx_device containing it's own internal queue.

I would have done this for Gallium first (EGL_IMG_context_priority) however Gallium driver relies on having a queue exist inside of agx_device. I'd think it would be reasonable for Gallium to have a queue per context (crocus appears to do this), but I am not familiar with the specifics regarding that.