[llvm] [GlobalISel][AArch64] AArch64O0PreLegalizerCombiner: Disable fixed-point iteration (PR #94291)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

Instead of the boolean `EnableFixedPointIteration`, I would prefer an upper limit on the number of iterations to have more control. The better question is how can we make fix-point integration a good investment. In which area of combines should we invest to still have significant combines in the last iteration?

https://github.com/llvm/llvm-project/pull/94291