Recommit "Transform vector SET{LE/ULT/ULE} -> SETLT and SET{GE/UGT/UGE} ->...

Recommit "Transform vector SET{LE/ULT/ULE} -> SETLT and SET{GE/UGT/UGE} -> SETGT if possible" (2nd Try)

Original version hit assert in `incDecVectorConstant` because VT could
be EVT (as opposed to MVT). Fix is to add check for VT.isSimple() in
`incDecVectorConstant`.

Reviewed By: saugustine

Differential Revision: https://reviews.llvm.org/D142254