aco: use saddr for global access with sgpr address

aco: use saddr for global access with sgpr address

fossil-db (Sienna Cichlid):
Totals from 38 (0.03% of 134621) affected shaders:
CodeSize: 237196 -> 237060 (-0.06%); split: -0.09%, +0.03%
Instrs: 43895 -> 43894 (-0.00%); split: -0.02%, +0.01%
Latency: 914633 -> 916263 (+0.18%); split: -0.01%, +0.19%
InvThroughput: 468215 -> 468971 (+0.16%); split: -0.02%, +0.18%
SClause: 1239 -> 1242 (+0.24%)
PreSGPRs: 997 -> 1003 (+0.60%)
PreVGPRs: 936 -> 923 (-1.39%); split: -1.50%, +0.11%

Regression seems to be RA noise, creating a waitcnt.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14124>