InstCombine: Fix layering by not including Scalar.h in InstCombine

(notionally Scalar.h is part of libLLVMScalarOpts, so it shouldn't be
included by InstCombine which doesn't/shouldn't need to depend on
ScalarOpts)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@330669 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed