[X86] Remove dead code for turning vector shifts by large amounts into a zero vector.

Pretty sure these are handled by a target independent DAG combine that turns them into undef these days.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321056 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed