nir: Move the compare-with-zero optimizations to the late section
nir: Move the compare-with-zero optimizations to the late section

total instructions in shared programs: 4422307 -> 4422363 (0.00%)
instructions in affected programs:     4230 -> 4286 (1.32%)
helped:                                0
HURT:                                  12

While this does hurt some things, the losses are minor and it prevents the
compare-with-zero optimization from fighting with ffma which is much more
important.

Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler