Revert "[asan-assembly-instrumentation] Prologue and epilogue are moved out from InstrumentMemOperand()."

This reverts commit 895aa397038b8de86d83ac0997a70949a486e112.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216872 91177308-0d34-0410-b5e6-96231b3b80d8