[X86][SSE] Update pshufb mask tests.
[X86][SSE] Update pshufb mask tests.

We are getting better at combining constant pshufb masks - use a real input instead of undef.

Add test for decoding multi-use bitcasted masks as well (actual support will come soon).

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@261101 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 192b67b57618ec4bc11ee54d4c7bc3b54878be11)

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm