[AMDGPU] Fixed test failure with AMDGPUPerfHint

We shall not keep iterator to a map while map is modified,
this leads to a broken map.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333298 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed