aco: optimize 32bit fsign by using fmulz with Inf
2 instruction fsign with the power of cursed DX9 floating point rules.
Foz-DB Navi31:
Totals from 3803 (4.86% of 78196) affected shaders:
Instrs: 8436366 -> 8412549 (-0.28%); split: -0.29%, +0.00%
CodeSize: 43174284 -> 43114676 (-0.14%); split: -0.14%, +0.01%
SpillSGPRs: 3241 -> 3247 (+0.19%)
Latency: 66333841 -> 66287361 (-0.07%); split: -0.08%, +0.01%
InvThroughput: 10331902 -> 10316916 (-0.15%); split: -0.15%, +0.01%
VClause: 165455 -> 165472 (+0.01%); split: -0.01%, +0.02%
SClause: 242352 -> 242335 (-0.01%); split: -0.02%, +0.01%
Copies: 604086 -> 605781 (+0.28%); split: -0.04%, +0.32%
Branches: 214017 -> 214013 (-0.00%)
PreSGPRs: 209413 -> 209726 (+0.15%)