[llvm] [AMDGPU] upgrade test to use auto-generated llc checks (PR #145832)

[via llvm-commits]

LuoYuanke wrote:

> Each of the update tools only checks the first line of the script. So to update for llc, you will need to switch that first line, run the llc update, and then switch the lines back. That last step is only for hygiene ... permanently switching the lines does not achieve much, and only adds a minor amount of noise to the diff.

It works. Thank you!

https://github.com/llvm/llvm-project/pull/145832