nir: Transform expressions of b2f(a) and b2f(b) to !(a && b)

nir: Transform expressions of b2f(a) and b2f(b) to !(a && b)

All Gen platforms had pretty similar results. (Skylake shown)
total cycles in shared programs: 532578400 -> 532578397 (<.01%)
cycles in affected programs: 2784 -> 2781 (-0.11%)
helped: 1
HURT: 1
helped stats (abs) min: 4 max: 4 x̄: 4.00 x̃: 4
helped stats (rel) min: 0.26% max: 0.26% x̄: 0.26% x̃: 0.26%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 0.08% max: 0.08% x̄: 0.08% x̃: 0.08%

v2: s/fmax/fmin/.  Noticed by Thomas Helland.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Thomas Helland <thomashelland90@gmail.com>