Revert "nir: Replace an odd comparison involving fmin of -b2f"

I originally noticed that 3b308147916 ("nir/algebraic: Optimize 1-bit
Booleans") caused this pattern no longer be matched by incorrectly
replacing b@32 with b@1.  Making that correct had no effect on
shader-db.  When this pattern originally was added, it only affected 4
shaders, so it's not worth the effort to debug further.

This reverts commit f50400cc8040cf2d07de97e76d9b1ed144c5c8b4.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6358>
(cherry picked from commit 314a40c902c6e92b9d6ba0e9b43708d7e1fa9f00)
2 files changed