[llvm] [NFC][AMDGPU] Do not flush after printing every instruction (PR #95237)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

I reverted, it's some weird interaction with the order in which the output is expected in the test.
I'm leaning towards guarding the flush calls so they only run in debug mode. I'll investigate a bit more in case I notice a better alternative.

https://github.com/llvm/llvm-project/pull/95237