[NewPM][AMDGPU] Skip adding CGSCCOptimizerLate callbacks at O0

The legacy PM's EP_CGSCCOptimizerLate was only used under not-O0.

Fixes clang/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp under the new PM.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D95250