[Flang][Pass]Disable memory intrinsics expansions
Patch disables memory intrinsics expansion, enabled by default in
https://github.com/llvm/llvm-project/pull/168622. This patch does the
same in clang, but not in flang.
The expansion causes massive perf regressions, up to 2x times in
fortran code.
Reviewers: jeanPerier, vzakhari
Reviewed By: vzakhari
Pull Request: https://github.com/llvm/llvm-project/pull/171650
