[CodeGenPrepare] Reverse the canonicalization of isInf/isNanOrInf (#81572)

In commit
https://github.com/llvm/llvm-project/commit/2b582440c16c72b6b021ea5c212ceda3bdfb2b9b,
we canonicalize the isInf/isNanOrInf idiom into fabs+fcmp for better
analysis/codegen (See also the discussion in
https://github.com/llvm/llvm-project/pull/76338).

This patch reverses the fabs+fcmp to `is.fpclass`. If the `is.fpclass`
is not supported by the target, it will be expanded by TLI.

Fixes the regression introduced by
https://github.com/llvm/llvm-project/commit/2b582440c16c72b6b021ea5c212ceda3bdfb2b9b
and
https://github.com/llvm/llvm-project/pull/80414#issuecomment-1936374206.