llvm/test/CodeGen/X86/shl_undef.ll: Tweak to satisfy r199050.

Use intel syntax, or "shl" might hit "pushl".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199051 91177308-0d34-0410-b5e6-96231b3b80d8