[AArch64] make test immune to scalarization improvements; NFC

This is explicitly implementing what the comment says rather
than relying on the implicit zext of a costant operand.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349166 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed