nir: Allow feq/fne/ieq/ine to be optimized with inot.
nir: Allow feq/fne/ieq/ine to be optimized with inot.

instructions in affected programs:     380 -> 376 (-1.05%)
helped:                                2

Reviewed-by: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>
Reviewed-by: Glenn Kennard <feea5431f8695a3af7470d472cb16ac8e02bab01@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler