[X86] Add a test case to show scalarized vector srem to demonstrate unnecessary instructions. NFC

After the division %ah is being sign extended to move it to lower byte of a register while avoiding a partial register read. We then zero extend the low byte to the full 32 bit register. But we don't use any of the zero extended bits. In the DAG the zero extend was really an any_extend so the sign extend should have been enough.

llvm-svn: 346580