[X86] Add -x86-experimental-vector-widening command lines to pmulh.ll
[X86] Add -x86-experimental-vector-widening command lines to pmulh.ll

I've only added sse2 and sse4.1 variants as I'm only interested in the two v4i16 tests and I don't expect that to different with AVX other than a v prefix.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@346834 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm