[X86] Add additional saturating add/sub vector tests; NFC

Additional tests for vNi32 and vNi64. I've added these for
usub.sat before, this covers uadd.sat, ssub.sat and sadd.sat.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351375 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed