[x86] More tweaks to the v32i8 test cases.

I made a mistake in the previous commit and produced the wrong pattern.
Fix that. Also make one more shuffle pattern byte-based rather than
word-based, and add two more blend patterns.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218439 91177308-0d34-0410-b5e6-96231b3b80d8