nir/algebraic: Replace a pattern where iand with a Boolean is used as a bcsel

nir/algebraic: Replace a pattern where iand with a Boolean is used as a bcsel

All of the affected shaders are in Mad Max.  I noticed this while
looking at some other things.  I tried a couple similar patterns, but
the affect on cycles was general negative.  It may be worth revisiting
this later.

v2: Rebase on 1-bit Boolean changes.

All Gen7+ platforms had similar results. (Skylake shown)
total instructions in shared programs: 15282073 -> 15282053 (<.01%)
instructions in affected programs: 1192 -> 1172 (-1.68%)
helped: 14
HURT: 0
helped stats (abs) min: 1 max: 2 x̄: 1.43 x̃: 1
helped stats (rel) min: 1.16% max: 2.17% x̄: 1.65% x̃: 1.39%
95% mean confidence interval for instructions value: -1.73 -1.13
95% mean confidence interval for instructions %-change: -1.91% -1.38%
Instructions are helped.

total cycles in shared programs: 372595954 -> 372594532 (<.01%)
cycles in affected programs: 11477 -> 10055 (-12.39%)
helped: 14
HURT: 0
helped stats (abs) min: 76 max: 122 x̄: 101.57 x̃: 104
helped stats (rel) min: 7.76% max: 15.62% x̄: 12.94% x̃: 14.78%
95% mean confidence interval for cycles value: -111.05 -92.09
95% mean confidence interval for cycles %-change: -14.90% -10.98%
Cycles are helped.

No changes on any Gen6 or earlier platforms.

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