Fix PR10475

Fix PR10475

- ISD::SHL/SRL/SRA must have either both scalar or both vector operands
  but TLI.getShiftAmountTy() so far only return scalar type. As a
  result, backend logic assuming that breaks.
- Rename the original TLI.getShiftAmountTy() to
  TLI.getScalarShiftAmountTy() and re-define TLI.getShiftAmountTy() to
  return target-specificed scalar type or the same vector type as the
  1st operand.
- Fix most TICG logic assuming TLI.getShiftAmountTy() a simple scalar
  type.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176364 91177308-0d34-0410-b5e6-96231b3b80d8