nir/algebraic: Mark some value range analysis-based optimizations imprecise

nir/algebraic: Mark some value range analysis-based optimizations imprecise

This didn't fix bug #111308, but it was found will trying to find the
actual cause of that bug.

Fixes piglit tests (new in piglit!110):

    - fs-fract-of-NaN.shader_test
    - fs-lt-nan-tautology.shader_test
    - fs-ge-nan-tautology.shader_test

No shader-db changes on any Intel platform.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111308
Fixes: b77070e293c ("nir/algebraic: Use value range analysis to eliminate tautological compares")
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>