nir/algebraic: Fix some 1-bit Boolean weirdness

nir/algebraic: Fix some 1-bit Boolean weirdness

Skylake, Broadwell, and Haswell had similar results. (Skylake shown)
total cycles in shared programs: 372594532 -> 372594460 (<.01%)
cycles in affected programs: 46854 -> 46782 (-0.15%)
helped: 9
HURT: 0
helped stats (abs) min: 2 max: 22 x̄: 8.00 x̃: 2
helped stats (rel) min: 0.02% max: 0.41% x̄: 0.16% x̃: 0.09%
95% mean confidence interval for cycles value: -14.34 -1.66
95% mean confidence interval for cycles %-change: -0.28% -0.04%
Cycles are helped.

Ivy Bridge
total instructions in shared programs: 12038379 -> 12038373 (<.01%)
instructions in affected programs: 1278 -> 1272 (-0.47%)
helped: 3
HURT: 0
helped stats (abs) min: 2 max: 2 x̄: 2.00 x̃: 2
helped stats (rel) min: 0.31% max: 0.77% x̄: 0.54% x̃: 0.55%

total cycles in shared programs: 180889027 -> 180888997 (<.01%)
cycles in affected programs: 29979 -> 29949 (-0.10%)
helped: 5
HURT: 0
helped stats (abs) min: 1 max: 16 x̄: 6.00 x̃: 5
helped stats (rel) min: 0.02% max: 0.34% x̄: 0.11% x̃: 0.07%
95% mean confidence interval for cycles value: -13.40 1.40
95% mean confidence interval for cycles %-change: -0.27% 0.05%
Inconclusive result (value mean confidence interval includes 0).

Sandy Bridge
total cycles in shared programs: 155091021 -> 155091003 (<.01%)
cycles in affected programs: 8842 -> 8824 (-0.20%)
helped: 2
HURT: 0

No changes on Iron Lake or GM45.

Reviewed-by: Matt Turner <mattst88@gmail.com>