nir/algebraic: Small optimizations for SpvOpFOrdNotEqual and SpvOpFUnordEqual

nir/algebraic: Small optimizations for SpvOpFOrdNotEqual and SpvOpFUnordEqual

No shader-db changes on any Intel platform.

Fossil-db results:

All Intel platforms had similar results. (Ice Lake shown)
Instructions in all programs: 144380118 -> 143692823 (-0.5%)
SENDs in all programs: 6920822 -> 6920822 (+0.0%)
Loops in all programs: 38299 -> 38299 (+0.0%)
Cycles in all programs: 8434782176 -> 8423078994 (-0.1%)
Spills in all programs: 206830 -> 204469 (-1.1%)
Fills in all programs: 318737 -> 313660 (-1.6%)

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12320>