Stop using radv_lookup_user_sgpr for the last pre-rasterization stage.
Tested on Ryzen 7 6850U: set the platform profile to performance, disabled boost and set the CPU governor to performance. Then ran: ./vkoverhead -test 0 -duration 30
| commit | 6850U score | 3700X score by @mbriar |
|---|---|---|
| main | 20772 | 17341 |
| radv: use direct access to last_vgt_api_stage_locs for sgpr emission | 20849 (+0.03%) | 21421 (+23.5%) |