[X86] Don't reuse an unrelated variable, create a new one. NFC.

Using Op makes it look like we're doing something with it.
We're really not.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260315 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed