Autogenerate headers for GPU commands / registers

Border line insane that we manually code up headers with register addresses / field locations and GPU command layouts. Worked on a bunch of hardware in my career (15ish years) and this is only piece of hardware where we didn't auto-generate headers for this stuff from the spec. AMD certainly appears to be doing this in their driver. This is something we really should consider at opening an issue so this doesn't get lost. Things like this are so much easier when the driver is small... Great intern project, in fact autogenerating code was my first project as an intern.