[CostModel][X86] Add SHLD/SHRD scalar funnel shift costs

The costs match the typical reg-reg cases - the RMW case can be a lot slower but we don't model that at this level

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346683 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed