[X86][AVX512] extend support in Scalar conversion
add scalar FP to Int conversion with truncation intrinsics
add scalar conversion FP32 from/to FP64 intrinsics
add rounding mode and SAE mode encoding for these intrinsics

Differential Revision: http://reviews.llvm.org/D12665

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248117 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed