nir: Rearrange bcsel with two bcsel sources

All Gen platforms had pretty similar results. (Skylake shown)
total instructions in shared programs: 14277220 -> 14277216 (<.01%)
instructions in affected programs: 422 -> 418 (-0.95%)
helped: 2
HURT: 0

total cycles in shared programs: 532577908 -> 532577848 (<.01%)
cycles in affected programs: 2800 -> 2740 (-2.14%)
helped: 2
HURT: 0

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