[llvm] [X86][AMX] Reserve all pair registers when AMXTRANSPOSE is not ready (PR #114706)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

@nikic Can you help to check if the change works? I tried to analyze locally, but `valgrind` doesn't work for me, and `timeit` has much noise. I checked it with `perf` and found the ratio of `LiveDebugValues` related functions were reduced with this change.

https://github.com/llvm/llvm-project/pull/114706