radv: round vgprs/sgprs before calculating max_waves

radv: round vgprs/sgprs before calculating max_waves

Note that ACO doesn't correctly round SGPR counts on GFX8/GFX9.

pipeline-db (ACO/Vega):
SGPRS: 11000 -> 11000 (0.00 %)
VGPRS: 3120 -> 3120 (0.00 %)
Spilled SGPRs: 0 -> 0 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 0 -> 0 (0.00 %) dwords per thread
Code Size: 164328 -> 164328 (0.00 %) bytes
LDS: 0 -> 0 (0.00 %) blocks
Max Waves: 1125 -> 1000 (-11.11 %)

v2: consider wave32

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>