[MemDep] Operand visited twice bugfix

Because operand was not marked as seen it was visited twice.
It doesn't change behavior of optimization, it just saves redudant
visit, so no test changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@290607 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed