radv/aco,aco: use scoped barriers

radv/aco,aco: use scoped barriers

fossil-db (Navi):
Totals from 109 (0.08% of 132058) affected shaders:
SGPRs: 5416 -> 5424 (+0.15%)
CodeSize: 460500 -> 460508 (+0.00%); split: -0.07%, +0.07%
Instrs: 87278 -> 87272 (-0.01%); split: -0.09%, +0.09%
Cycles: 2241996 -> 2241852 (-0.01%); split: -0.04%, +0.04%
VMEM: 33868 -> 35539 (+4.93%); split: +5.14%, -0.20%
SMEM: 7183 -> 7184 (+0.01%); split: +0.36%, -0.35%
VClause: 1857 -> 1882 (+1.35%)
SClause: 2052 -> 2055 (+0.15%); split: -0.05%, +0.19%
Copies: 6377 -> 6380 (+0.05%); split: -0.02%, +0.06%
PreSGPRs: 3391 -> 3392 (+0.03%)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4905>