[llvm] AMDGPU: Fix temporal divergence introduced by machine-sink and performance regression introduced by D155343 (PR #67456)

[via llvm-commits]

petar-avramovic wrote:

blockPrologueInterferes in tryToSinkCopy seems to be required,
For example see _amdgpu_ps_main2 from llvm/test/CodeGen/AMDGPU/sink-after-control-flow-postra.mir 
blockPrologueInterferes stops sink of 
renamable $sgpr0_sgpr1 = COPY $sgpr6_sgpr7
past its use $sgpr4_sgpr5 = S_AND_SAVEEXEC_B64 $sgpr0_sgpr1, implicit-def $exec, implicit-def $scc, implicit $exec

https://github.com/llvm/llvm-project/pull/67456