nir/algebraic: Pull common multiplication out of flrp arguments

nir/algebraic: Pull common multiplication out of flrp arguments

All Intel platforms had similar results. (Skylake shown)
total instructions in shared programs: 15342485 -> 15337495 (-0.03%)
instructions in affected programs: 217456 -> 212466 (-2.29%)
helped: 1539
HURT: 1
helped stats (abs) min: 1 max: 17 x̄: 3.24 x̃: 3
helped stats (rel) min: 0.22% max: 18.75% x̄: 3.10% x̃: 1.91%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 0.56% max: 0.56% x̄: 0.56% x̃: 0.56%
95% mean confidence interval for instructions value: -3.39 -3.09
95% mean confidence interval for instructions %-change: -3.24% -2.96%
Instructions are helped.

total cycles in shared programs: 355734320 -> 355728237 (<.01%)
cycles in affected programs: 1851555 -> 1845472 (-0.33%)
helped: 835
HURT: 575
helped stats (abs) min: 1 max: 658 x̄: 40.62 x̃: 14
helped stats (rel) min: <.01% max: 35.69% x̄: 3.78% x̃: 1.81%
HURT stats (abs)   min: 1 max: 322 x̄: 48.40 x̃: 14
HURT stats (rel)   min: 0.04% max: 71.02% x̄: 8.06% x̃: 2.43%
95% mean confidence interval for cycles value: -8.50 -0.13
95% mean confidence interval for cycles %-change: 0.48% 1.62%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).

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