[AVX-512] Add separate ISD opcodes for each form of CVT instructions. Don't reuse non-X86 ISD opcodes with extra X86 specific arguments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282230 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed