spriv: Produce correct result for GLSLstd450Step with NaN

spriv: Produce correct result for GLSLstd450Step with NaN

NOTE: This commit needs "nir: All set-on-comparison opcodes can take all
float types" or regressions will occur in other Vulkan SPIR-V tests.

No shader-db changes on any Intel platform.

NOTE: This commit depends on "nir: All set-on-comparison opcodes can
take all float types".

v2: Fix handling 16-bit (and presumably 64-bit) values.

About 280 shaders in Talos are hurt by a few instructions, and a couple
shaders in Doom 2016 are hurt by a few instructions.

Tiger Lake
Instructions in all programs: 159893290 -> 159895026 (+0.0%)
SENDs in all programs: 6936431 -> 6936431 (+0.0%)
Loops in all programs: 38385 -> 38385 (+0.0%)
Cycles in all programs: 7019260087 -> 7019254134 (-0.0%)
Spills in all programs: 101389 -> 101389 (+0.0%)
Fills in all programs: 131532 -> 131532 (+0.0%)

Ice Lake
Instructions in all programs: 143624235 -> 143625691 (+0.0%)
SENDs in all programs: 6980289 -> 6980289 (+0.0%)
Loops in all programs: 38383 -> 38383 (+0.0%)
Cycles in all programs: 8440083238 -> 8440090702 (+0.0%)
Spills in all programs: 102246 -> 102246 (+0.0%)
Fills in all programs: 131908 -> 131908 (+0.0%)

Skylake
Instructions in all programs: 134185495 -> 134186618 (+0.0%)
SENDs in all programs: 6938790 -> 6938790 (+0.0%)
Loops in all programs: 38356 -> 38356 (+0.0%)
Cycles in all programs: 8222366923 -> 8222365826 (-0.0%)
Spills in all programs: 98821 -> 98821 (+0.0%)
Fills in all programs: 125218 -> 125218 (+0.0%)

Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Fixes: 1feeee9cf47 ("nir/spirv: Add initial support for GLSL 4.50 builtins")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13999>