[x86] Fix a bad predicate I spotted by inspection -- pshufhw and pshuflw
were added in SSE2, no SSSE3. Found this while auditing all uses of
SSSE3 in the X86 target. I don't actually expect this to make
a significant difference on anything and I don't have any detailed test
cases but I updated the existing test cases that already covered some of
this code path.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209056 91177308-0d34-0410-b5e6-96231b3b80d8