intel/fs: limit register flag interaction of FIND_*LIVE_CHANEL

What does this MR do and why?

intel/fs: limit register flag interaction of FIND_*LIVE_CHANEL

Those instructions do not access the flag registers on Gfx8+. Removing the interaction enables CSE to remove more of those instructions.

Results are a bit mixed :

ACO:

Totals from 127 (5.97% of 2128) affected shaders:
Instrs: 139966 -> 138972 (-0.71%); split: -0.85%, +0.14%
Cycles: 1685747 -> 1667480 (-1.08%); split: -2.35%, +1.26%
Max live registers: 10582 -> 10544 (-0.36%)
Max dispatch width: 1048 -> 1040 (-0.76%)

Cyberpunk 2077:

Totals from 2879 (27.95% of 10301) affected shaders:
Instrs: 4264789 -> 4225666 (-0.92%); split: -1.01%, +0.09%
Cycles: 72380209 -> 71619521 (-1.05%); split: -1.63%, +0.58%
Subgroup size: 30624 -> 30632 (+0.03%)
Spill count: 98 -> 101 (+3.06%)
Fill count: 90 -> 93 (+3.33%)
Scratch Memory Size: 8192 -> 9216 (+12.50%)
Max live registers: 217807 -> 217098 (-0.33%); split: -0.59%, +0.26%
Max dispatch width: 23792 -> 24112 (+1.34%)

Gaining 40 SIMD16 shaders

Rise Of The Tomb Raider:

Totals from 622 (5.06% of 12289) affected shaders:
Instrs: 437380 -> 434760 (-0.60%); split: -0.72%, +0.12%
Cycles: 261843085 -> 261580703 (-0.10%); split: -0.73%, +0.63%
Max live registers: 27731 -> 27766 (+0.13%); split: -1.01%, +1.14%
Max dispatch width: 5832 -> 5432 (-6.86%); split: +0.27%, -7.13%

Loosing 26 SIMD32 shaders

Strange Brigade:

Totals from 1298 (31.48% of 4123) affected shaders:
Instrs: 1504408 -> 1487968 (-1.09%); split: -1.17%, +0.08%
Cycles: 20735976 -> 20443216 (-1.41%); split: -1.60%, +0.19%
Max live registers: 89911 -> 89957 (+0.05%)

shader-db DG2 :

total instructions in shared programs: 23130895 -> 23130036 (<.01%)
instructions in affected programs: 260956 -> 260097 (-0.33%)
helped: 234
HURT: 101
helped stats (abs) min: 1 max: 54 x̄: 6.36 x̃: 4
helped stats (rel) min: 0.05% max: 8.16% x̄: 2.01% x̃: 1.90%
HURT stats (abs)   min: 1 max: 37 x̄: 6.23 x̃: 3
HURT stats (rel)   min: 0.02% max: 5.67% x̄: 0.89% x̃: 0.55%
95% mean confidence interval for instructions value: -3.62 -1.51
95% mean confidence interval for instructions %-change: -1.33% -0.94%
Instructions are helped.

total loops in shared programs: 6071 -> 6071 (0.00%)
loops in affected programs: 0 -> 0
helped: 0
HURT: 0

total cycles in shared programs: 898610645 -> 898557166 (<.01%)
cycles in affected programs: 18308201 -> 18254722 (-0.29%)
helped: 315
HURT: 48
helped stats (abs) min: 1 max: 19312 x̄: 404.23 x̃: 128
helped stats (rel) min: 0.02% max: 28.98% x̄: 3.92% x̃: 2.65%
HURT stats (abs)   min: 2 max: 14478 x̄: 1538.60 x̃: 409
HURT stats (rel)   min: <.01% max: 23.24% x̄: 3.34% x̃: 0.41%
95% mean confidence interval for cycles value: -333.68 39.03
95% mean confidence interval for cycles %-change: -3.51% -2.41%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 5964 -> 5964 (0.00%)
spills in affected programs: 0 -> 0
helped: 0
HURT: 0

total fills in shared programs: 6909 -> 6909 (0.00%)
fills in affected programs: 0 -> 0
helped: 0
HURT: 0

total sends in shared programs: 1040266 -> 1040266 (0.00%)
sends in affected programs: 0 -> 0
helped: 0
HURT: 0

LOST:   3
GAINED: 1