aco: CSE iadd and uadd_carry

fossil-db (navi21):
Totals from 5 (0.00% of 135636) affected shaders:
Instrs: 7851 -> 7783 (-0.87%)
CodeSize: 43828 -> 43560 (-0.61%); split: -0.62%, +0.01%
Latency: 382660 -> 382416 (-0.06%); split: -0.07%, +0.00%
InvThroughput: 238335 -> 238173 (-0.07%); split: -0.07%, +0.00%
VClause: 271 -> 269 (-0.74%)

fossil-db (vega10):
Totals from 1 (0.00% of 134698) affected shaders:
CodeSize: 7900 -> 7904 (+0.05%)
Copies: 157 -> 156 (-0.64%)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Closes: mesa/mesa#5545