radeonsi: set no-signed-zeros-fp-math

radeonsi: set no-signed-zeros-fp-math

Recommended by Matt Arsenault.

46757 shaders in 28742 tests
Totals:
SGPRS: 2068851 -> 2066907 (-0.09 %)
VGPRS: 1604056 -> 1602676 (-0.09 %)
Spilled SGPRs: 1402 -> 1382 (-1.43 %)
Spilled VGPRs: 113 -> 113 (0.00 %)
Private memory VGPRs: 1332 -> 1332 (0.00 %)
Scratch size: 3224 -> 3188 (-1.12 %) dwords per thread
Code Size: 58815520 -> 58716788 (-0.17 %) bytes
LDS: 1162 -> 1162 (0.00 %) blocks
Max Waves: 354616 -> 354905 (0.08 %)
Wait states: 0 -> 0 (0.00 %)

Totals from affected shaders:
SGPRS: 786452 -> 784508 (-0.25 %)
VGPRS: 530000 -> 528620 (-0.26 %)
Spilled SGPRs: 958 -> 938 (-2.09 %)
Spilled VGPRs: 85 -> 85 (0.00 %)
Private memory VGPRs: 636 -> 636 (0.00 %)
Scratch size: 1880 -> 1844 (-1.91 %) dwords per thread
Code Size: 26349936 -> 26251204 (-0.37 %) bytes
LDS: 304 -> 304 (0.00 %) blocks
Max Waves: 108962 -> 109251 (0.27 %)
Wait states: 0 -> 0 (0.00 %)

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>