[AMDGPU] Precommit some scheduler related test updates

Summary:
The point of this is to make some tests with manual checks robust
against scheduler tweaks, so that only autogenerated test updates will
be required when pushing D68338 "[AMDGPU] Remove dubious logic in
bidirectional list scheduler".

Reviewers: arsenm, rampitec, vpykhtin

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75302