[llvm] [GlobalIsel] Combine freeze (PR #93239)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

For poison tests, AARCH64 registers are treated as poison. Using G_CONSTANT as parameters might trigger other optimizations. G_CONSTANT_FOLD_BARRIER(G_CONSTANT) is not a constant and not poison.

https://github.com/llvm/llvm-project/pull/93239