intel/fs: Use De Morgan's laws to avoid logical-not of a logic result on Gen8+

intel/fs: Use De Morgan's laws to avoid logical-not of a logic result on Gen8+

Instead of emitting ~(a & b), emit (~a | ~b) since logical-not of
operands is free on Gen8+.

v2: Fix swizzles.  Fix types for cmod propagation.

v3: Simplify logic for inverting source of inot(ixor(a, b)).  Suggested
by Ken.

Skylake and Broadwell had similar results. (Skylake shown)
Skylake
total instructions in shared programs: 15185593 -> 15185583 (<.01%)
instructions in affected programs: 5673 -> 5663 (-0.18%)
helped: 12
HURT: 1
helped stats (abs) min: 1 max: 2 x̄: 1.17 x̃: 1
helped stats (rel) min: 0.30% max: 5.88% x̄: 1.50% x̃: 0.70%
HURT stats (abs)   min: 4 max: 4 x̄: 4.00 x̃: 4
HURT stats (rel)   min: 0.12% max: 0.12% x̄: 0.12% x̃: 0.12%
95% mean confidence interval for instructions value: -1.66 0.13
95% mean confidence interval for instructions %-change: -2.60% -0.15%
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 370977726 -> 370964249 (<.01%)
cycles in affected programs: 869987 -> 856510 (-1.55%)
helped: 15
HURT: 2
helped stats (abs) min: 2 max: 6640 x̄: 902.20 x̃: 16
helped stats (rel) min: <.01% max: 4.92% x̄: 1.71% x̃: 1.53%
HURT stats (abs)   min: 14 max: 42 x̄: 28.00 x̃: 28
HURT stats (rel)   min: 1.08% max: 3.18% x̄: 2.13% x̃: 2.13%
95% mean confidence interval for cycles value: -1654.87 69.34
95% mean confidence interval for cycles %-change: -2.29% -0.23%
Inconclusive result (value mean confidence interval includes 0).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>