[llvm] [NFC][MISched][AMDGPU] Expose tracePick to be used in AMDGPU backend (PR #184664)

[via llvm-commits]

lijinpei-amd wrote:

> Reasoning should be given when closing PRs

The pr tries to fix 3 minor points in GCNSchedStrategy:

1. tracePick is not called as in the general MachineScheduler.
2. do-while on condition that should be asserted. This is already changed in MachineScheduler.
3. Candidate reason not accurate.

As these points are minor, I think it is not worthwhile to pursuit it.

https://github.com/llvm/llvm-project/pull/184664